What you're reporting is indeed a bug, but it doesn't have anything to do with the forums, per se; it's my server, and this happens across all the sites that I host where the server will randomly bork form submissions by dropping the connection
I am sorry about it, and I am looking into, but it's really difficult to troubleshoot since it appears to be random, and only seems to happen to me when I'm really busy and can't shoot it down in the moment.In the meantime, even when the server doesn't do this, given the lack of auto-save on posts/PMs, I've always recommended that folks write their messages in an email or other document editor that does have auto-save, and then paste the message into the forum editor when you're ready; if something happens, you just re-load the form and paste again. I've looked into adding an auto-save feature to the boards, but the last time I looked it took too much work to accomplish.