Absolutely! The real complexity comes from conflict resolution. If someone edits the top, and someone else edits the bottom, which version do you go with? What if they're editing the same area? Entire companies exist to provide elegant solutions to this[0], so it's no simple task.

0: https://liveblocks.io/

yourworldoftext is kind of in this space, although it's not traditional HTML. In it's heyday there were a lot of internal pages that were kind of like wikis

Something like etherpad? https://etherpad.org/

See https://etherpad.wikimedia.org/p/hello-hackernews for a real-time demo (works better with more people, I suppose!)

ProseMirror (an excellent library IMO, though it takes a couple of hours of reading the docs to get started) has support for collaborative editing: https://prosemirror.net/examples/collab/

I work for XWiki SAS. Two products we develop have it:

- XWiki, a extensible wiki platform, experimentally [1] but soon to be fully supported.

- CryptPad [2], an end-to-end encrypted collaborative platform. And actually, CryptPad was accidentally born as a first attempt to have this feature in XWiki.

[1] https://extensions.xwiki.org/xwiki/bin/view/Extension/Realti...

[2] https://cryptpad.org/