Interesting, I did not know that. But I don’t think it’s relevant, none of them have bad eyesight, and they also make heavy use of backgrounds that make things harder to read (though, maybe CS counteracts the issue).

I think people who aren't sufficiently tuned into computer geek and/or Web and/or font nerd culture are aware that they're supposed to think Comic Sans is bad, and instead they like it. I see it used all the time, in many contexts, by people who seem to just think it's fun.

I notice often when other people have worse eyesight then me, it wouldn't surprise me if you're unaware of how good your eyesight actually is and/or your friend believes their eyesight is at least above average (at least with glasses) when maybe it's not.