I've long noticed the connection between liking fountain pens and mechanical keyboards, but never noticed the tie to head phones. (I'm sitting here wearing some.)
Maybe the personality trait influencing this is a higher sensitivity to tactile experience. I wonder what other tastes this group might share. Of course, nice notebooks/pads go with the pens. I have an inclination toward boardgames with hefty dice, and I'm very choosy regarding my coffee mugs.
There's a good chance you could finally be the push to get me to post on /r/mechanicalheadpens and subscribe. I've been on all three individually for years and known about /r/mechanicalheadpens for about as long, but never really thought about it as being its own community rather than just a novelty until seeing it in this context.