I hope this helps identify the issue of the duplicate posts we're seeing around here so often.
I've noticed it happens more frequently when I get a notification while I'm writing a message in the same topic. I've also noticed that when it happens, there is a much higher chance of a duplicate posting if the server goes down.
If had had to guess (in spite of my limited qualifications), it seems that traffic intensity is a part of the issue.
I won't be adding much, if anything, to this, since, as I said, this is not my area of expertise.
Lehi