what do the thread icons mean?

Specifically, in the "Common Lisp" forum, the "What are you doing in Common Lisp lately?" is tagged with a circular field of scrolling text, with a red star in it. () I've deduced that the star means "you've posted in this thread", but that thread is the only one I can see with the scrolling text icon. The URL of the image (topic_read_hot_mine.gif) seems to indicate "hotness" of the thread -- who designates that? Me or a forum owner?

Just curious.

I think it means it's hot. It's driven either by views or by the number of postings. I can't tell which. As near as I can tell, you can't control it. It's part of the theme, I think.