Messages that have been queue for moderation can appear in one of two places:
Forum posts: https://www.virtualmin.com/admin/content (or click "Content" in the top menu bar when logged in with the necessary privileges to moderate content)
Forum comments: https://www.virtualmin.com/admin/content/comment (or click "Content" and then the "Comments" tab)
Messages that have been queued by the spam filter will be labeled "Not Published". Those are invisible to users.
Steps to take when spam happens
Report to Mollom
If you see spam, click the far-right "Report" link at the bottom of the message first. This will pop up a modal to allow you to choose why it's being reported. This adds the message to our spam corpus (we use Mollom for this). This will help prevent future messages that look similar. It currently catches maybe 80% of spam that comes in.
Report to StopForumSpam
After reporting to mollom, click on the username to browse to their account. Click on the "Spam" tab.
If the user has made multiple posts, presumably all spam, check a few of the boxes (not more than four or five, though, as it ends up leading to false positives based on the IP address being reported multiple times), and then click "Block" at the bottom. This will unpublish *all* of their messages (even the ones you didn't check) and block the user.
If you feel ambitious and have time to kill, you could then go through a report a few of the others to Mollom, but I usually just do the first one I see, since spammers often post the same kinds of things multiple times.
If you're unsure if it's spam
Sometimes people make a spammy post that is questionable (hosting offers, etc.). If they've got the spammy bit in their signature, I might remove the signature, and see if they stick around or continue to make questionable posts. If they are answering questions sincerely (and not just copy-pasting from some other random comment to make it look real), it may be worth keeping them around, even if they are being pushy about marketing. There's some kind of limit, and it's rare for someone who legitimately wants to help out to be too pushy about it. We welcome folks to make money using Virtualmin; and we welcome folks to offer contracting and other services in our forums, as long as their posts are relevant and not overly spammy. Sometimes, I'll catch a hosting provider pitching their services, and they don't even offer Virtualmin! They usually get the boot, because they're just here to spam.
Feel free to escalate to Joe, if something seems amiss but you're not sure what to do about it.