We've seen it here, but if you have posts auto-moderate with certain phrases (probably happens regardless), the bots have begun to get past this buy posting something simple that won't trigger most of these filters and then immediately editing the post to insert their spam posts.
Quite an annoying tactic that you may want to watch out for.
May be something of this sort: If a new member adds a link or attachment via edit, it automatically pushes it to a moderation queue. Would such a feature have drawbacks if implemented as a core feature?
Then these spammers are manual spammers and they have no issue to pass the filters from the first place.
I really don't understand the "spammers" problem. Never had them. Just use KeyCaptcha or other flash/HTML5/JS based Captcha and they will never come to your board. Using Captcha based on question/numbers/letters is a pure fail.
Yes, this means that it works as designed. But the design overlooked an issue which makes the functionality have a loophole. So, not a bug by definition but still something that would be nice if its fixed.
I have very few spammers that even get through all the ip and email checkers. Then akismet is checking their post. It's usually a out of place post anyway so If I see a weird post I check the IP, Google the username and ban if I find even one spam post on Google or even a better sign is finding an account link on Google for that name and then the account doesn't exist anymore when you click it. Means they were already banned elsewhere. Plus I don't allow edits of posts or much else till 20 posts.