What is the difference between, say, the effects "Reduce Perception" and "Damage Perception". Is it like in Oblivion/Morrowind where "damage" is permanent and reduce is the same as drain, i.e. temporary? Because the effects for the poison "Mother Darkness" has Damage Perception & Agility by 3 for 60 seconds, which would be overkill if it was permanent, so I assume that damage is only temporary and reduce is redundant.

This was puzzling enough to make me look at in the geck.

There are indeed 2 base effects, one being ReducePerception and one being DamagePerception.

ReducePerception has the Hostile flag unchecked, and the Recover flag checked. DamagePerception has the opposites on those flags. Other than that they are identical.

I've not personally used such things but, it seems that one looks more weapon-like and one looks more ingestible-like.

So, understanding the nuances of what those flags mean would be the key to this whole picture (I am not all the way up on them).

That makes sense, that reduce is used for ingestibles, and damage is used for poison/object effects (hostile actions).

On a semi-related note, I find it odd that all the damage fatigue weapons utilize a script to accomplish this and then have a "dummy boxing glove" effect. As I write this it occurs to me that this is to hide the amount of fatigue damage that is being done. I couldn't figure out how to do the same thing with a poison, which is what made me look into it. But I could make a new effect to damage fatigue (which oddly didn't already exist).

You culd try it, but.

So far in my travels, when the game's devs do something unconventional, it's because the thing one would have expected to work either didn't, or it didn't work well enough, or it didnt work AS well.