Playtest
    -Savrethi nuisance doesn't flow well as a topic, specially in sentences. You can just use his name tbh, or maybe no proper nouns at all, just something unique enough.
    -If you drink the potion directly after taking on the quest, then talk to the questgiver then to the wise woman, the reply she gives is: "As I said before, you will need evidence..."
    -I suggest you not make the options not this obvious in the journal. It feels kinda railroady. Generally, the journal should not say what the player didn't think of.(Not a hard and fast rule, but a good filter)
    -The journal should prolly have a bit more detailed directions to the source.
    -The script for the source isn't working, more info in the scripts section.(Atleast in OpenMW)
Dialogue
I like the tone you go for a lot!
    -Generic dialogue(not for a particular id) should generally have a NoLore filter. (Sometimes, like with slaves, you may have to skip that because almost all of them have nolore.
    -For slaves you might have to take into account Khajiit, which might benefit from their style for speech.
    Topic Mandaras Savrethi
    -"The Hlaalu are rarely respectful of our customs, but that man is more fool than most.", fool->foolish
    -"...I hear his crops are struggling as of late. How fortunate." same as above for the earlier thing, also I don't think the crops will struggle as fast. The sentence also feels a bit off.
    -"Excellent! Here, take this poision to the source. ..." 
    Topic Savrethi Nuisance
    -As said before, this topic will be better merged to Mandaras Savrethi or at the very least have it's name changed.
    -"I see, I hope that you will see sense and reconsider..." Full stop after see.
    -"Hush now, not so loud. The tribe is thankful for your actions, thought they cannot know it." thought->though
    -"His accursed distillery saps the water that is ours by right and his farming disrupts the ..." gluttony and subterfuge feels a little too mordern, specially for ashlanders. Also, this is a little too overdramatic imo. The ashlanders care more about ancestor worship and traditions rather than opposing immoral acts like Gluttony and greed, if that makes sense. Even if this is just supposed to be his own ideas, it'll be better toned down a bit.
    -"Choice "Yes" 1 "No" 2" needs full stop after Yes and No
    Greeting 5
    -"Welcome to our tribe, Outlander. Be courteous and act with respect and you shall be welcomed. Unlike that Savrethi nuisance." Outlander shouldnt be capitalised.
    Journal
    -The name should be "TR_m4_Ob_name" because the quest is started in Obainat camp.
    -Journal indices 45 and 200 should have finished checked, while 35 shouldn't.(35 should allow persuing other things, I might even say that it doesn't require a journal, it's more of flavor dialogue.)
    -I haven't seen indices as big as 1000 used, but it's not really an issue, just kinda unusual.
    (Other couple things in Playtest section)
Scripts
    -The scripts should not have the same name as the object, can lead to some errors iirc. Just use _sc/_scr in the end.
    -The script name should generally be TR_m4_q_PW_name (_q is optional, and PW is a shorthand for your quest) (ideally even the object ID will be good this way, but not required)
    -if (menumode == 1)
            set pcskipequip to 1
                if (onpcequip == 1)
                    startscript, tr_m4_poisonhelper
                        if (getjournalindex "tr_m4_poisoning_the_well" != 0)    
                                if (getjournalindex "tr_m4_poisoning_the_well" < 40)
                                    journal "tr_m4_poisoning_the_well" 40
                                    set tr_m4_hibdun_drank to 1
                                endif
                        endif
                endif
        
    endif
    is better indented as
    if (menumode == 1)
        set pcskipequip to 1
        if (onpcequip == 1)
            startscript, tr_m4_poisonhelper
            if (getjournalindex "tr_m4_poisoning_the_well" != 0)    
                if (getjournalindex "tr_m4_poisoning_the_well" < 40)
                    journal "tr_m4_poisoning_the_well" 40
                    set tr_m4_hibdun_drank to 1
                endif
            endif
        endif
    endif
    (counting if-endif is easier)
    -The spacing needs to be consistent. Eg  ( MenuMode == 1 ) has spaces next to brackets, but  (doonce == 1) does not. The latter and the others should have one. Also, seperating different blocks by a line makes it more readable.
    -player->removeitem "tr_m4_hibdun_poison" 1) has extra ) at the end in TR_m4_savrethi_source. (one of the these two fix the issue.)
    -You don't need to have three different blocks for the if ( DoOnce == 0 )...
        if ( doonce == 0 )
            If ( getjournalindex "tr_m4_poisoning_the_well" >= 20 )
                If ( getjournalindex "tr_m4_poisoning_the_well" <= 35 )
                    if ( player->GetItemCount, "tr_m4_hibdun_poison" == 1 )
                        If ( GetDistance, Player <= 512 )
                            set boxactive to 1
                            set doonce to 1
                        endif
                    endif
                endif
            endif
        endif
    -Also, the above blocks had an extra endif.
    -'short helperhelper' is moot in TR_m4_Poisonhelper
    -"short potCheck" is moot in TR_m4_Savrthi_Source.
    -TR_m4_Poisonhelper has an extra endif.

Dialogue
    Topic Poison the Water
    -"...Here, I have a few leftover potions I stashed away from the same place I got the poison. I feel you have earned them more than I." Nitpicky, but 'I feel' doesn't suit his character imo. 'I think' or just 'You have...' is better. 'I stashed away from the same place I got the poison' also is off. You could probably cut that part, or atleast rephrase.
    -The dilogue filters should be from top to bottom without gaps (Convention + it's easier to check if you accidentally removed something and such) (Specifically speaking about the nolore checks)
    -"You poisoned the Savrethi's water supply? ..." remove 'the'
    -Subterfuge feels really mordern to me, still feel like it should be changed, specially for ashlanders.
    -'TR_m4_Ob_Hibdun_Senatmiran->ModDisposition -40' the name doesn't have _Ob so the whole result doesn't work for "You poisoned the Savrethi's water supply?..."
    Topic Mandaras Savrethi
    -"...I plan to poison the water supplying his precious plantation, ..." this isn't gramatically correct. It should be 'the water supply of his plantation' or '(the source) that is supplying the water'. The former is probably preferable, because it fits the topic.
    Greeting 5
    -A greeting like "I asked you do poison the water supply, didya do it?"(With better wording :P) would be great for the middle portion where he only has generic greetings.
    Journals
    -Journal 15 should have finished checked, and 20 should have restart(so if the player doesn't want to take the quest at that moment, it won't get stuck in the journal.)
    -Journal index 12 needs a comma after however.
    -Same thing as topic Mandaras Savrethi's in index 20 about 'the water supplying the Savrethi Distillery' 
    -'Wise Woman Musa' is better phrased as 'the wise woman, Musa Ashadallit' imo. It might look repetetive, but the player will see maximum two entries with her name.
Scripts
    -The spaces are still not consistent, maybe you're editing somewhere else and it's getting messed up in copy-paste?
Playtest
    -IMO you shouldn't be able to complain to Musa after drinking the poison before talking to Hibdun(and after)(because you can't really get evidence, and there's no reason to complain now imo.). This is just my opinion, do what you feel is right.
    -The waterfalls are basically impossible to get to with low acrobatics, and it looks kinda ugly near the rocks in OpenMW(Not your fault, just ask to change a bit it in merge notes)
    -The 'base' of the waterfall could be construed as the pictured place, so might want to rephrase that.
    -A lot of the slaves have NoLore(all of non-khajiit ones i think.), so either remove nolore(exception to the rule here), or just remove said dialogue.
    -If you don't wanna worry about disease or being naked being an issue, use greeting one for goodbye greetings.(use it rarely, only when it's needed)

-Missed this last time, but the entry which first references 'poison the water' "He has been causing frustration...", and the greeting which introduces Mandaras Savrethi (the third greeting 5) should have addtopic "Topic Name".
-Generally, using the full name is prefered in journals(even in other dialogue, but more in Journals). (It's easier to recollect for the player if they spent a lot of time in between strating the quest and finishing it, and it's a precedent.)
    -"Don't involve me in Hibdun's antics. If you must tell someone go to Musa, our wise woman." is a good non-journal example to add the full name, because this could be the first time the player heart of Musa.
-You missed a couple of entries for the ending NoLore (Namely the last two on Mandaras Savrethi)
-'Excellent! Here, take this poison to the source. It's the large waterfall just to the Northwest', northwest shouldn't have a capital N.
-"Wonderful! Excellent work. You have done the right thing for the tribe and for the land. ..." A full stop instead of a comma after here fits a bit better.
-You missed subterfuge in the nerevarine version, and missed adding the full stops in non-nerevarine choices.
-Also, there is a missing 'I' in "Although know the tribe leaders would not sanction such subterfuge" (Nerevarine version)
-"...Thank you for your honesty %PCname, I think a small reward is in order...." A full stop instead of a comma after %PCName (both versions)
-"...Hibdun is known to be hot-headed, I'm sure his threats were hollow.", A full stop instead of a comma after hot-headed.
-"Hush now, not so loud. The tribe is thankful for your actions, though they cannot know it." maybe add 'about' before 'it'?
-"Truly? You might as well try to tell Mandaras, but don't expect a warm welcome, you'll find him on the top floor." Full stop instead of comma after welcome.
-"Welcome to our tribe,... " The ending, 'Unlike the Hlaalu nuisance Mandaras Savrethi' is just kinda off. Maybe a rephrase would help?
-Topic Mandaras Savrethi-> "...Unfortunately, I know the tribe would never allow it." add 'that' after know.
-I feel like a wise woman wouldn't say "n'wah". Tbh doesn't even need a special case for dumner, although I wouldn't mind if it did fit.
-The journal should have 'poison the water' and preferably 'Mandaras Savrethi' somewhere in either journal 10 or 20 so it gets highlighted in the journal.
-This is really subjective, but imo with all the dialogue in the distillery, it creates an impression that there is some content there. *Maybe* it'd be better if no one pointed his location out.(The slave's dialogue seems fine, I'm specifically talking about the nobles')

Review
-"...mentioned that he has plans to poison the water that supplies the plantation. ..." and "...poison the water that is supplying Mandaras Savrethi's distillery..." the 'water' is being supplied, not supplying, if that makes sense. I'm not even sure supply is the right word to use here
-"... It is a simple request, but one that has proven far too difficult for Mandaras Savrethi to grasp." add 'people like' before 'Mandaras'
-Really small thing to keep in mind, for scripts and stuff capitalising TR everywhere in 'TR_m4_...' is more uniform.
-Add full stop to the choices in "His accursed distillery saps the water that is ours by right and ..." non nerevarine version.
-Due to how the cells are divided, the slaves don't have any dialogue.(Cause they aren't in the cell.)
-I wonder if having the pond as the place to poison it will be better. Not for the showcase, but a thing to think about.

-Removing some of the dialogue in the Mandaras plantation will make it better imo.
-"... The rest is spent keeping those bothersome Ashlanders away." change dialogue
-"Hibdun Senatmiran was delighted that I completed the task for him and rewarded me with several potions from his collection." collection feels kinda off for this.