I'm also noticing that, when posting, I sometimes receive a popup from my browser (firefox) asking for permission to move away from a page (with one option to continue, and one not to).
Selecting the option to continue is what is necessary to actually post (selecting the other allows continuing to edit). The catch is, on an increasing number of occasions, selecting the option to continue results in TWO copies of the post appearing in the thread. When I see those within the permitted period, I delete them.
Same happens if I edit one of my posts - so I can duplicate a post by attempting to edit it. Or have two slightly different versions of a post.