I think if those accounts still have their regular website link then all of such accounts should be compiled and reported to theymos either as a PM message or maybe via this thread. It will be much easy for him to manually remove those links if word-filters aren't working the way they were supposed to work.
I don't think that the solution is that theymos or mods go from profile to profile and delete the website link from the profile. I believe that it is possible to do it through the forum administration, I guess maybe directly through the database.
Even if we find all mixer accounts, what prevents them from opening new accounts and adding a link to the site in their profile? And yes, for better SEO, this item certainly matters when it comes from a high DA site like Bitcointalk.