Although I kind of, almost agree with Doppleganger, I think there's shades of blame here that have to be considered.
The rule from the FAQs concerning Signatures, that was mentioned was one designed with a specific purpose. A board has to try to avoid getting too cliquey. What I mean is you hope to avoid a board becoming a place where only certain groups can feel comfortable posting, or a certain group, or groups might gain the kind of power where they can decide what, or who can or can't post or be posted. Every one should feel comfortable putting forward their little theories or whatever.
At the same time though a person wants to feel comfortable making friends, and expressing that connection.
It's like, suppose the board administrators decided to ban these kinds of threads as a matter of policy. First of all I would say it probably isn't necessary, because I don't think this is a particularly cliquey board, so I wouldn't see the necessity of another rule. I would find it overly authoritarian - a little goose-steppy. And how far do you want to take it? Do you want to ban comments in posts that suggest a connection between 2 or more members? Do you want a board where it's one homogenized, unfriendly mass?
Personally I view these kinds of threads as something just making it on this side of the scales in the balancing act between cliquey and homogenized. As such my impression is they're tolerated, more than endorsed.