I've noticed a bug on 4.1.3. If the message takes longer to post (for example if you have multiple URL's inside your post), it's auto creating a double post divided by the automerge line. Probably because the forum is trying to get all URL titles, it takes a while... and the Doublepost Prevention consider it as multiple post or something
I hope this can be fixed. Thanks!
P.S. In the attached screenshot you can see a sample. I only posted once but appearead as double post merged. Tested again and it happened the same.