Why would anyone ever approve a comment from a keyword name? It’s obviously spam. If it is a real name with a “spammy-ish” site, I’ll simply manually remove the URL when I approve the comment.
I recently tweaked a bot-trap and some php to have comments on my blog submitted to the IP address of the visitor to the site. If they submit a comment to a different IP address, they are blocked.
Example: My IP address is 184.108.40.206. When I want to post a comment on my blog, the (form) will submit the comment to 234.2342.2342.234.php. Since the formname and my IP match, the comment is handed over to Akismet and WordPress. But then if someone later tries to submit a comment to that IP address, (like say a spider that crawled my site gathering comment form submission URLs) they will be instantly blocked when they submit. It’s been working pretty well.
Also, anyone that tries to submit to the default WordPress post comment URL is blocked automatically.