yes, I really want this hack too. I actually did that once (placed a user on everyone's ignore and disabled their option to view it) and it was very effective. I got a new troll now on my bb that needs just this kind of treatment
Anyhow, Konqueror, go for the usergroup version. This way, you can simply change your code to use $bbuserinfo[usergroupid] and $post[usergroupid] -- these variables are already pre-loaded so there won't be any additional queries to make.