As far as acid splash is concerned it still says you stepped in acid, but it never damages you.
I thought acid is not ment to damage you but lower your AC by 2 or so. I feel like I saw this somewhere written ingame but I am not sure.
Yes, I read the same. I also hope that the ground effects will wear off eventually in the game. If there happens to be a bottle or barrel of water available it can wash away grease at least. I assume it would do the same for acid.
