It's not weird at all. It seems a bit rude, though, to make such a comment without defining why you find it so strange, so "weird", don't you think?

Let me try and explain why there's nothing odd about it, why it's actually quite normal and rather mundane.

A long time ago on message boards of the internet people would post about topics they were interested in discussing with others who found such topics interesting. Oftentimes many people who were interested would join in, sometimes only a few. In either case, ideas specific to the topic were exchanged.

Back then, people would browse the message boards for particular topics they were interested in and could constructively contribute to. Topics they weren't interested in and couldn't contribute to constructively would usually be passed by for some other specific topic that interested them.

There were of course the net.weenies but they were few and rather far between.