It doesn’t have to be. You just need copy-paste to a pastebin or upload site, and need clients to support embedding content.

Then it doesn’t matter how each client does it.

This already works between Textual, IRCCloud, QuasselWebserver, and a handful more.

So now I need yet another service, which may not be accessible to the other people.

I'm going to stick with the one that does the things that I want it to do now, and doesn't require me to hope that the other person can see what I'm trying to post.

You mean, you’re going to stick with the one where you rely on a central authority, all your data is accessible to them and the intelligence agencies of their country?

There’s a major tradeoff to be made there.