I would have thought that that would be over by now. Surely all of America is online by now already?

Eternal September doesn't have to do with new users to the internet, but new participants within a community.

It's essentially the problem of digital immigration (which is much easier to do than physical immigration).

I would argue that new users on a forum that have already used other forums will be easier to integrate than those who have never been online before. And those that have used multiple forums will be easier still as they will be used to the idea that different communities have different rules.

Why?