I seem to have a related problem. Some comments are marked as spam on my site after they have been edited even though that should not be the case.
I cannot really say why this is happening, but it is happening especially when someone posts a long comment on the site and then edits it.
An example is this comment: http://www.ghacks.net/2014/02/21/telegram-questions-answered-whatsapp-messenger-alternative/#comment-1993903
It was marked as spam and I had to move it mark it as legit so that it would appear on the site.