Reproduction steps:
1. Disable scripting in your browser
2. try to edit one of your existing posts
3. upon submission (pressing the “OK” button), user is returned to the editing interface without the changes applied to the published post.

Not everyone has scripting available, not everone has it unavailable through choice. Not all browsers support it (Lynx), some firewalls are configured to strip/block scripts.
You cannot rely on JavaScript being available. Period.

You are very right/ Less than 2% doesn't have it available, so I'm willing to take the risk.

Furthermore: then forum is developed by the BOINC developers, not by me.

May I ask where you get <2% from…?

May I also ask why accessibility in general is of such little concern?

Oh, come on. The time of the text based browsers is long time over Nowadays almost everyone and every site uses JS like it or not The fact that mobiles have support for JS speaks for itself...

To be fair, the current BOINC code used on projects does not display this problem. The issue is that in forum_edit.php, a JavaScript based redirect is used here on BoincStats. Everything in the BOINC source repositories indicate that all the project forums are using a HTTP-based redirection. I even checked to see if this behavior had changed from an old version of the server code but as far as I saw, it did not.

I'm guessing it was changed like this because some HTML output from the BoincStats header was already sent by the time the forum code calls for a HTTP redirect. In PHP, this is not allowed unless output buffering is turned on (off by default). The alternative is to move the redirection logic before any HTML output is sent in the forum_edit.php script.

Also in terms of consistency, current BOINC forum code still puts in place noscript fallbacks for some JS-dependant things like the Edit/Reply/Send Message form buttons recently introduced on the forum_thread.php page.

Everyone has JS enabled, and mobile browser developers add JS support, BECAUSE of these retarded websites that don't work without it.

Fixed this problem.