I think it would be a good idea to provide information on what actions gain/lose piety with deities. Looking at the wiki, a lot of the information is out of data or untested. It will always become obsolete every time you make a change anyway.
It seems we have to do a lot of un-fun in-game research (restarting many many times) before we can make an informed choice as to whether to follow a certain deity. Monster stats are visible, the exact effects of items are visible. Why so cagey about the gods?
Just to stress this point. This is not a minor issue for me. I cannot play this game with the free time I have available without access to accurate information about the gods.
Another problem with this secretive approach is we can't report bugs if we don't know how things are supposed to work.
I just got cursed by Tikki Tooki after I killed a monster without taking a single hit. It was the second monster I killed in that dungeon and I had not been hit once. Is this a bug? No idea. I don't know what Tikki Tooki punishes you for.