Sometimes (eg. [this question](https://stackoverflow.com/questions/4598254/svn-create-a-dump-file-of-a-folder)) more than one user will simultaneously attempt to edit a post, particularly to fix poor formatting by the OP. It looks like in that case, I finished 30 seconds sooner than @marcog, but I don't know who might have clicked "edit" first.

Anyway, a useful usability enhancement would be to keep track of who is (or might be) editing a post at any given time. With this enhancement, the second user to click "edit" might see something like:

> 
> The following users may currently be editing this post:
> 
> 
> * marcog (21 seconds ago)
> 
> 
> 

If a message like that were available, I would immediately choose not to edit at that time, and maybe come back later if the formatting still needed fixing. This saves effort, frustration, and duplicate "hey I fixed your formatting" comments.

It is important to note that this feature would not attempt to *prevent* multiple editors, everything else would work just the same as it does now.

Implementation idea
-------------------

This feature could be implemented by adding a new table, say "editors", with the columns (post\_id, edit\_start, user\_id). When a user clicks "edit" on a post:

* Check the editors table for old entries for this post, say > 5 minutes. Delete them.
* If there are any current editors, show the list as above.
* Insert a row for the current post and the current user with the current time.

When a user submits changes to a post:

* Delete the user's record from the editors table for that post.

Periodically:

* Scrub old entries from this table (if a user clicked "edit" but never submitted a change for that post).

Optionally:

* Provide a "Cancel" button on the edit page. Cancelling would remove the current user's record for the current post, but obviously not submit any changes.

---

**Update**: After saying in the comments that I've never seen the edit notification, I actually did just get it today editing [this question](https://stackoverflow.com/posts/4600351/revisions). However, it showed the orange bar at the top (1 other users edited!) for a *brief* time just *after* I pressed "Save". What good is that?