What happens is that the forum database periodically needs to be reindexed. If we don't catch it often enough, the forum can get very sluggish. cgi actions during this sluggish period can take forever, and if you hit "Submit" multiple times, which is the temptation while you're waiting, you will get multiple posts.
As phranque suggests, when this does happen, or when you see a dupe, it would help us a lot if you used the "report msg" link to the left of the post. Ditto regarding other discussion problems on the thread.
Msg#: 4635450 posted 7:46 pm on Jan 7, 2014 (gmt 0)
Our system shows that only one post by you was removed from the above thread.
I see you also had a duplicate removed from another thread [webmasterworld.com...] around Jan 1. Here's the time signature I'm seeing for the post on the US Pacific coast...
3:15 am on Jan 1, 2014 (PST -8)
Also, its a bit weird that edit post (as opposed to reply) can create a dupe - surely it is tied to a post ID?
phranque would know more about the back end mechanisms than anyone else here would. I suspect that the sluggishness of the system may also have something to do with the load on the server at the times you've experienced the problem.