Thanks for your reply. What I do is: click on 'Reply', write my comment (or paste it, considering all the troubles I've had, I've also tried writing it in a text editor and then pasting it into the message box), and then click on ‘Add Reply’. I get a red bar error message at the bottom saying that there was a problem posting my reply and to try and contact an administrator if the problem persisted. The messaged appeared at the bottom of the page, and automatically disappeared after a few seconds. It wasn't the usual notification about message moderation, but a specific error message. This happened regardless of which editor I used (standard, advanced, in source mode or in preview mode). After the fifth failed attempt even with a different browser, I gave up.
However, I just tried now and this time it worked, so I cannot reproduce it anymore. Probably something related to the error timed out.
