I occasionally downvote a few (3-5) of your comments in a row, based on merits, not anything else, but I haven't done it recently, so someone else might be expecting you to post low-quality comments and, after stumbling over one, goes through a bunch. I wouldn't sweat it, though. I think I dropped 10-12 karma in the last couple hours, probably for similar reasons. Just do your best to make useful and measured comments and the forum readers will appreciate it.