I was thinking that an effective measure to keep the robots out of a webmaster forum may be to insist on a unique email domain per user registration.

Any webmaster must own a domain name or 10, so it is easy for them to create a forwarding email @ their domain in order to register with sites.

But the bots may tend to use free email services. And if they use the domain of their master, then he/she may be concerned to be hunted down and dealt with accordingly.

A further step might be to use the rep score of a user to determine if their posts are visible to the public, and encourage forum users to use the rep system to inform the community that the member is ok and unlikely to be a bot. So the up and down votes would be totaled, and each user would only be able to adjust their vote between -1, 0, and +1 per member that they voted on. So no one user can ramp up the rep of another. Then there would be a rep threshold to enable public visibility of the member's posts.

So if the good bot later turned into a bad bot, their posts could still be blanked out at a later date if their rep sank below the threshold. Or their signature links were blanked out along with their recent posts. Moderators could maybe revert their status to noob if they turned bad, allowing for a period of reflection and to be given another chance.