paf127 wrote:

Something like this happened to me on 2013-11-18 here:
https://www.mediawiki.org/w/index.php?title=Project:Support_desk&lqt_method=talkpage_history

As you can see I also got 4 copies. I believe I was blameless; I only clicked once. I was using Firefox 25.0 on Microsoft Windows 7.

My uncertain recollections are as follows:

• Clicked "Start a new discussion".
• Did some typing.
• Would have done at least 1 preview of the new thread.
• Would have clicked "Save page".
• I have a feeling that if I was distracted and looked away from the screen at that point, and then looked back at it, there was no indication that the upload was still in progress. I think I had to scroll up a bit and could then see some spinning icon.
• I was surprised at how long it was taking, but I waited.
• I think with no further intervention from me, eventually a new page loaded, but with just 1 copy of my new thread.
• I think it was only later, when I was doing an edit of my post, that I noticed that there were 4 copies of the thread.
• So I renamed & blanked 3 of them.
• At that point they seemed to disappear from the list.
• I can see in the talkpage_history page that 12 hours later someone deleted them for me.

Bug 29786 would presmuably deal with the symptoms of this.