But the community would be a subreddit, not the site reddit.com, which is far too heterogeneous to be considered some kind of community.

That was the idea years ago, but they completely abandoned it.

https://archive.vn/KojNR#selection-7875.0-7947.5

Brief recap on its current state of affairs: https://www.youtube.com/watch?v=wqx4wdn4Odc (18 minutes and change)

You'd be surprised what percent of reddit visitors just browse popular or don't do specific subs outside the default. Most users aren't super users.

That's probably true, but people who just look at popular post and aren't engaged in anything aren't really part of any community either, unless we expand community to literally mean anybody that's visiting the site, at which point it becomes somewhat meaningless because it's too homogeneous again.

Terms that have no distinctive power have little value, so while I'd certainly consider them "users", I wouldn't consider them part of the community, much like a tourist staying in a village for a weekend isn't a part of the village's community.

I don't go to my city council meetings, but am still a member of our local community.

This is quick becoming a debate over definitions, but I think reddit thinks of itself as both having a community and also as having individual communities. For example, anybody who has had a post in their niche community get to the front page understands that there's a larger community they're a part of that is different from their smaller one.

Sure, much like you can get your 15 minutes of fame and get on national TV. I wouldn't call "the whole country" one community with smaller child communities though.

To me, community implies some amount of connections between the members. I've never put a number on it, but basically something like "if you randomly pick X people from the group, at least Y of them will know each other". That would limit both the size and also do a reasonable test for community membership: if nobody in the community knows you, you're not a part of the community.