A couple weeks back I drafted up a post. I ended up not posting it (because I didn't think it was a good enough contribution to take up space) and didn't attempt to make any posts in that thread until today.
Today I wrote a new post in that thread. I started by using the "Quote" function along with "open in a new tab." (I do this so I can draft a response while continuing to read the thread, then post if it's not a topic that's been covered already.) So, new tab that's just a blank slate for my response.
So after I posted today's post, I went and checked the thread, and somehow my account had made two posts, one which was today's post, and one which was the never discarded draft from a few weeks ago.
Not sure if I described what happened or how very well, sorry.
Edit: This was on a Win7 PC running chrome.
What is this I don't even.