I just realized that Ideatorrent allows some HTML in the comments, but I can't find any documentation. http://blog.qa.ubuntu.com provides a list of valid tags underneath their comments box, and this should be provided on Ideatorrent, too.
(I will test in the comments below this to see if the same subset of tags work. In the rationale descriptions, links and images seem to be the only things supported. Italics, bold, blockquote.