Collaborating on Discord is fine. Important results, including citations backing them, should really be published or at least replicated in more durable medium that's less susceptible to link rot, and easier to archive. Today, that's PDFs in paper repositories, or even regular blog posts.
The right way to reference scientific publications is by URN [1], not URL. That makes the location irrelevant, as it should be.
I'm not sure that they're collector's items, but they're probably not in that many university libraries. For example, the University of Michigan library has a physical copy in its special collection, but my university's considerably smaller library does not. But that's just because of age: this is a 119-year-old paper; were it a little younger, say, about 70 years, it would be in my university's holdings. I think that's a considerably different order of magnitude of its lifetime from a Discord link that I'd be absolutely astounded to see last a decade, and that in practice will probably last much less time than that.
I was a grad student at the institute for theoretical physics in Heidelberg. It's famously housed in two old villas with little room for books, so all the walls in almost all rooms are lined with shelfs. In the office I shared with five other students, there was one shelf in it that was locked. The only one in the building. In it was one book from 1905 that had a different color than all the others.
That's the physical copy of the papers you mean. They had issues with theft so they had to have it replaced and then lock it. It probably wasn't even original though.
so clearly discord is inherently different and here to stay forever! /s
feels like time is a circle sometimes ha
It’s shuttering.