Invisibilty

[Batman?]

I caught permanent invisibility drinking from pools. Does being invisibile carry an experience penalty when fighting monsters? In reading the wiki its says no, but I feel like that is innacurate. Is there any way besides pools to get rid of it?

[Grond]

Wiki is correct in this case. It also has an accurate answer to your other question.

[Batman?]

That seems super overpowered. Being invisible gives you a large offensive advantage without an experience penalty. The few instances where its a problem (shopkeepers) seems very manageable unless you get the condition early in the game. Am I missing something?

[Grond]

Invisibility is indeed a very strong ability. Some people find it annoying due to the way it changes monster behavior, but that's a very subjective "problem". In general, you don't get experience penalties for being OP; speed is the exception, not the rule.

[auricbond]

I'm unaware of any content you're locked out from due to being invisible except the arena, which can be a significant penalty early-game.

Superoverpowered is the norm in ADOM. I once got a surge of power bracers of war in my first ten minutes of playing. Enjoy it.

while it lasts...

[Blasphemous]

Sometimes rng lures you into these early artifacts - I once got skullcrusher and serpent's bite both in UD within 20 minutes of a new game. Died in HMV to a stone giant lord rock, thrown from outside of LoS.
As for invisibility, I prefer temporary, on-demand one. Permanent has some subjective disadvantages - many times I want monsters to see me and come straight at me, while some monsters, which I'd prefer not to notice me, see through invisibility by default.
I role-play to some extent and feel uncomfortable stealing stuff from shops, which is the default action when invisible and unspotted.
High stealth is much more preferable than invisibility to me.