dusky - 11:10 pm on May 8, 2010 (gmt 0)
g1smd, yes /path-does-not-exist [L] is a direct response without a redirect, nonetheless will produce a 404 error header, whether that is custom error or the raw webserver 404 response.
As to the A-Za-z instead of A-Z, I was intending to catch both lower and higher case spam / wrong keywords or parameters, but I guess I am not an expert on the subject and the [NC] is enough to cover both and only serve/ catch one instance.
The important thing, in my opinion, is NOT to serve the content of /keyword-title/ when /keyword-title/?q=spam-keyword is requested.
Exactly, as in most cases it's a hack attack / injection attempt or someone trying to frame you with SEs. It is different from /wrong-keyword-title/ posted as a backlink (or accessed as such) instead of /keyword-title/ which one should redirect it to the correct page /keyword-title/ instead of serving a 404 error response.