In discussion based settings, the only time I’ll raise my hand, is to signal to the teacher (moderator) that I wish to speak. Usually this only occurs if I feel like the person talking is making a lot of points that need to be addressed, without letting anyone else get a word in. Does this make sense? I will also use hand-raising as sort of a signal to the person, that there are other people who wish to speak. I think it really depends on the setting of the discussion. Generally I feel like it’s rude to raise my hand while someone else is speaking, if I wish to be recognized to speak next, I will make an attempt to signal the teacher (moderator) without being as obvious as raising my hand.