That would make a really cool advanced feature! I suspect that's pretty niche, however, and I definitely think the future of the platform is in easy to handle, automatic notifications though, which is why I think this is so great.

A crystal clear statement of intent, and a working implementation of notifications, with one very clear caveat where we're saying, hey Lemmy devs, help us implement this without the security concerns.

Maybe one day you could offer private notification servers as a free option, and your own servers as an Apollo-like subscription cost/one time fee (if costs are low enough)? I definitely want to see this project stay economically viable so we can continue to get the great dev work you've been doing so far!