I don’t think this is an internet thing per-se.

I don’t think this is an internet thing per-se. What you describe seems to happen with subcultures in general, but the internet increases speed and scale so that these tendencies are amplified (and does a lot of the time-binding necessary for creating institutional memories useful for inter-group rivalries automatically).

4chan & other imageboards are an interesting case regarding time binding because they don’t typically have a good archive facility the way their most direct competitors (reddit-alikes and discussion forums) do & they lack reasonable logging defaults the way that irc does (while irc servers don’t keep logs, every irc client has a logging facility and most enable it by default, so any conversation on irc is probably being logged). This means that the institutional memory is being cultivated by insiders — even the parts of it that are used by outsiders — which is a little like a secret society publishing heavily-redacted copies of its meeting minutes. But the upper limit on speed and scale on imageboards is so much higher (and effortposting / reading the whole thread is considered a newbie mistake, further accelerating this) that both the mutation rate of cultural signals and the degree to which those signals get overemphasized is much larger.

We’ve had heavily intellectually-incestuous groups in the past, often driving big major cultural forces. We call them art movements or skunkworks. Now nearly every affinity group is like that because communication is fast and cheap. The material impact of this change in scale will probably have even stranger side effects than the ones you describe here.