Right now what I'm able to reproduce is:
Open a page in a tab (tab #1), start typing an answer but don't submit.
Open the same page in another tab (tab #2).
In tab #1 submit the answer.
In tab #2, click the reply box, you see the answer that was already submitted.
Obviously that's an edge case that doesn't make much sense in day to day use, but I'm suspecting that this is the kind of thing that may happen when I have a tab where I've started to reply, then I get a notification, click the notification and that opens a new tab with that same page...