I have just asked a question (which is somewhat of a rarity for me) in a sub-thread, and having recieved an answer, I just wouldn't feel right if I didn't thank the person publicly who answered my question.

Had I asked in a root node, I wouldn't post a thank-you to everyone who responded. I'd probably pick one of the best answers and thank them, with "thanks also to..."

As an answerer-of-questions, I like to be told if my answer did, or didn't help the poster. Thanks aren't required, "That worked" is good enough for me.

Update: Fixed link ++ kyle && planetscape