This answer was supposed to be an edit of prior answer, but the software incorrectly posted it as a new answer.

Update I found another probably related problem - see my comment to Jeff's answer. Now I am reasonably sure that this is a bug in the software, viz. the software can be in some inconsistent state if one uses "Back" in the browser.

• I edited an answer of mine a few minutes ago and had no troubles... It's going to be hard to fix if it is hard to reproduce. – Arturo Magidin Jan 28 '11 at 17:09
• do you mind doing the following (for the benefit of the presentation of the website)? Please add a comment on the "original question" pointing to this thread on Meta, and please "delete" the "original question". Anyone who can do something about this problem will have either sufficient reputation or moderator privileges that he/she can see the deleted answer. And this way it doesn't confuse the new users. – Willie Wong Jan 28 '11 at 18:46
• @Willie: I left the duplicate in case it can be of use for debugging. I'll delete it later. – Bill Dubuque Jan 28 '11 at 20:09

I'm with Robert -- this is a mistake based on accidental use of the back button. I can duplicate this if I use the back button to go back after posting.

In other words:

3. Click the back button and "edit" your post (you are not in fact doing so..)

This results in a duplicate answer.

I just verified this on dev, and I produced a duplicate answer with the above steps, as we've seen before.

So, be careful with that back button. If you want to edit a post, click the edit link.

• Ok, I've verified that this does cause a duplicate post in the version of Chrome I'm using. But I'm fairly sure that's not what happened in my case. If it was that simple I'd have encountered it before in my 500-odd posts since I use browser Back (and Forward) heavily. Perhaps something changed recently on SE that triggers it in my use patterns? In any case since I can't reproduce what was the actual cause I suppose we'll have to consider it nonreproducible. But I'll keep me eye out for a reproducible instance in the future. – Bill Dubuque Jan 29 '11 at 4:30
• Update: I found another (perhaps related) problem. I mistakenly posted a comment as an answer. I deleted the answer. When I attempted to post the comment it asked if I wanted to post another answer (so it seems the page was in some inconsistent state). I believe I had used browser "Back" to get to that page. So the problem may be that "Back" can sometimes leave things in an inconsistent state. Alas, I had no luck reproducing this problem either. But I have no doubt something in the software (vs. I) was confused. – Bill Dubuque Feb 5 '11 at 23:34

This "bug" is reported on rare occasions and each time we were able to trace the problem, it turned out the user was clicking the browser's 'back' button to edit the post instead of clicking the edit link. If you click the 'back' button, edit, and click `Post Your Answer', you will be posting a new message.

There has never been a case of being able to reproduce this behavior, otherwise.

• I'm not sure if that explains it or not. I will try to see if I can reproduce it that way. – Bill Dubuque Jan 28 '11 at 19:42