Sometimes you see some of the most obviously painful questions in the forums and you scratch your head, did that person just ask that publicly.

A Google Webmaster Help thread has one person asking if “backlinks from forum profile” can hurt him.

John Mueller from Google responded directly and clearly that it can hurt you. He wrote:

One of the more common manual actions I see are those with forum links, to be honest. Just stay away from it.

Forum discussion at Google Webmaster Help.