I've been having this problem where, when I do the quick reply, it will make me double post. I'm not clicking the button more than once. Just, sometimes it will take a really long time to load, and then when I go back to view the post, there will be two of them. This is irritating, and I'm not sure if it's a problem with my computer, or with the site. I've never had a problem with this on other forums.
This is a symptom of site performance issues. I've pointed out response issues to Daniel recently, and he's looking into them. All I can suggest is to be patient. I remove double posts when I see them, but I'll mention it again to make sure he looks into that aspect specifically.
The same thing happens to me, but it usually gives me a "You cannot post two messages within 15 seconds of each other [sic]" error.
