Well, take a look at the user profile of empegbot, the source is listed there.

I didn't look at it intensively and I don't know JavaScript anyway, but it seems to basically post a reply using the the normal web interface for replies of the BBS to inject its random texts to the BBS.
If you want to know how he could change the original posters BBS name with the "eb does not reply to anyone" text, just take a look at the HTML code of the normal reply page. All necessary input is right in there.

BTW: This could also (and pretty easily AFAICT) be used for a nice add on to the UEBBS: It could be used to provide a mail interface to the BBS with some lines of perl, leading to an immediate (bi-directional) link between the BBS and a mailinglist. Another TODO on my list, I guess.

cu,
sven