Treat 'f' randomly generated in a dungeon as any other creature. Slay them with extreme prejudice.
If you get a wilderness enounter of cave lion, leave them alone.
If you make it to cat lord, you normally don't really need the ring, but might need the XP. If you die before reaching the catmeister, you did not lose anything, and saved yourself some major hassle. If you died because you tried something cute to avoid killing a cat, well then you just lost a potential YAVP.
For me the cat ring is a "challenge" game, on par with "bringing joy to the life of a little girl" or "defeating an emperor minotaur".
Mabye I'm more a dog person.
ADOM General's warning: Treasure Hunting causes slowness, frailty, terrible markmanship and is dangerous to your characters' health