Urgh. Bumping in groups & Q&A are NOT the same - putting "bump" in an answer in Q&A does NOT move it to the top, like in groups. You cannot "bump" a question in a reply. You can hit the bump button, and questions that have multiple bumps appear in a special list, but you cannot move a question. In groups, putting bump in a reply does move it to the top.
at 11:50 AM on Apr. 26, 2011