First, you can personally ignore a new user who makes inane comments.
True, but even on Reddit using RES, ignoring users became fruitless over the last year. Too many to ignore in most threads that giving up Reddit was easier than ignoring 50 dipshits per comment section. In smaller niche subreddits, sure it was still doable, but I found it to become fruitless, and removing myself from the community became easier than trying to stay on top of ignoring and filtering people. The way I saw it, is if I have to ignore more than half the users I came across, then maybe I'M the one who was in the wrong place.
I don't doubt MK could come up with something to improve the quality of the site if there were to be a huge influx of users, but other than a small pay-wall and stiff moderation like SomethingAwful, I've never seen a website sustain high quality forums for discussion as they've become more popular. He'd be the first person, in my opinion, to truly solve that issue if he did.
Reddit did a decent job up until subreddits were hitting hundreds of thousands of users, and some with moderation even kept them decent at that point. But when the defaults toppled into the millions not even moderation could stop how crummy they got. And those users from the defaults just assumed that kind of crap was acceptable everywhere on the site, and the same type of behavior spilled into even the smaller and more niche subreddits.
So we'll see, but yes I have faith in MK too, but it's still a huge challenge should this site get large. In the mean time I'm going to enjoy the quality and lack of ass-hattery of a small community. :)