>HN users have an intense emotional relationship with the front page
If a "greatest 80s hits" radio station started broadcasting music from the 00s and people got pissed off you wouldn't say "listeners of this station have an intense emotional relationship with it". When they tune in to the "greatest 80s hits" station, that's the only thing they're looking for; they don't want to listen to random songs.
There are risks to making too many rules about who gets to be a member in your club.
Just for clarity, when I was talking about how users are emotional about the front page and react intensely when they see something they don't think belongs there, it was in the context of an experiment we'd run to randomly place stories from /newest on the front page. Users reacted disastrously, not so much because of scope but because the median article's quality is just really low. That's true about in-scope topics like programming as well as other topics. I hope that makes sense.
As for 'who gets to be a member' - we don't restrict that nor want to restrict that. Everyone with intellectual curiosity, i.e. everyone, is welcome. The only requirement is actually using the site in that spirit. This is not so easy, of course, especially when the more activating topics show up.