I have an RPG environment and I'm looking for words that sound better than "buff" for positive modifier and "debuff" for negative modifier. I simply don't like the words but I'm having a hard time finding more appropriate words.
Buff/debuff seems like a good pair of words for the enhance/downgrade contrast that the terms stand for in role-playing games, and they probably are well understood in that environment. You might consider unbuff in place of debuff. Some other possible or impossible pairings: tune/detune, amplify/attenuate, raise/lower, boost/unboost, trim/pare, furbish/disfurbish, augment/deduct, add on/strip, upgrade/downgrade, enhance/detract.
I saw this post awhile back and wanted to leave my own little something for future readers. In the internal engine that the game Everquest and Everquest 2 uses, the enumerations that signify buffs is labeled as "Beneficial" effects, and Debuffs are internally referred to as "Detrimental" effects. Buff and debuff is just a slang word used by the community of players.
I'm not an RPG player, but my first instinct is to agree with you that "buff" is a poor choice of word insofar as it doesn't fit in with any of the story genres I see RPGers play in. "Debuff" isn't in my vocabulary.
The most generic, commonly used word I can think of is "enhance", and I suggest you consult a thesaurus for its synonyms.
A suitable opposite might be "degrade" or "diminish", and again, I suggest you consult a thesaurus.