Sorry I cannot yet reproduce this all the time, it has happened a couple of times for me when typing a post and using the return key (on a Mac keyboard), instead of moving the cursor down a line it actually posts the uncompleted post, in other words it is activating the "create thread" button.
I wasn't sure if this is a bug at first, or me accidentally hitting some other key as well which is supposed to activate that button.
How would that be possible while I'm actually typing, I tried to do and
click somewhere else in the browser window and can't get it to happen yet it sometimes just happens randonmly while typing and hitting the
It could be down to another key being hit (tab would move you out of the field for example) or some sort of key combination that causes the browser to submit the form. There isn't any code that programmatically submits the form when you're in the editor.