I recently started using IRC again (I joined a small channel because of a random event). Surprisingly the magic is still there for me.

>besides, those people are largely reachable on slightly more modern services these days

The thing is, people are NOT reachable on IRC in general. They join when they wake up (or return from school, or return from work). When they leave you can't contact them (and you can criticise/praise them freely if you want). Sometimes a new person joins and never returns again. Sometimes they join tomorrow, the day after, and become a regular. Other times someone starts joining less and less frequently, then one day leaves and never returns.

People say "hi" when joining and "bye" when leaving.

I'm general, I realized this is much more similar to talking with real people than modern groupchats. Of course this is just a protocol, and nowadays this behavior is just a choice (everyone can install a mobile client and stay always online. Even back then it was possible with a bouncer). But I'm surprised how invested I became in this micro-community, in a way i never would on a discord server.