Maybe they know something you don't. Maybe they saw what you missed? Maybe John having a different opinion than you is simply that?
Also in general speaking, I find it hard to believe that a true mafia would post so little. It's probably something like the idea that... 'there are so many of us, so few left of them, my vote isn't going to matter much, I think I'll stay out of the drama and let the bored people do my work for me.' Apathy is the word that comes to mind, someone who's busy - but they're isn't a pressing need for them to maintain a presence.
I would think a mafiaperson might just stay in mid-range of activity level, not too much, not too few. (RB / BH.) Ricket's 4 posts a day (and thanks to HN for pulling all of them) which include 2 word responses... that's not someone with any role in this game to protect.
So who's pulling midrange and submarining topics...