> But, given that the proper format for email bugs is unlikely to be present
> in run-of-the-mill spam, one would guess that a fairly simple filter
> might weed out the vast majority of spam sent to the bug-reporting
There are two problems with this. First, $email@example.com accepts absolutely freeform email messages to followup to existing bug reports. So that's hundreds of thousands of email addresses spammers could still send spam to, even if firstname.lastname@example.org has smart filtering.
Secondly, all it takes is a few spammers who set up a targeted spam template with the appropriate headers for submit@, and suddenly we have to deal with not only large volumes of incoming spam, but spam that creates new bug reports that choke up lists of the real bug reports. So I think it's smart to not force the spammers to learn how to do that.