Note: Brownies ARE sidhe, and saying the TY word to a brownie is one of the worst personal offenses you could do toward them. It is HORRENDOUSLY culturally insensitive to ‘thank’ a brownie.

Note that most, though not all, of the sidhe fall into the DA classification. So if it is a white arts ‘faie’ and not a brownie, leprechaun, or amadan then you are most probably safe. Though I would imagine that leprechauns would let this offense go as spirits.