Mastodon is a more mature software so they probably had more time to work on extra features like cross-platform federation.
You would think so, but afaik Mastodon hasn't made any changes to federation in years. Which means it is left to other projects like Lemmy to reverse engineer whatever Mastodon is doing and implement that, no matter what the standards say.
Lemmy actually marks votes as private for federation, but it seems that kbin/mbin ignore that.
I think Lemmy is attractive enough, but that only matters when people actually want to join something new. Thats currently not the case, so for better or for worse we have to wait for another wave.
Users need to be approved by a mod before they can follow, browse or post in the community.
I could certainly see a feature like this implemented as a plugin. But it would need someone to volunteer for the programming work.
I think no one ever opened an issue for such a feature, so please go ahead and do that.
Posting links with no attached (body) text
We could easily add a community setting to make the body mandatory. I suggest you open an issue for that.
This, now we have school holidays and my kids are home 24/7. Takes a lot of time and energy to keep them entertained.
I am planning to implement private communities soon, hopefully it can help with that. Then maybe Lemmy can become an alternative for Discord and other platforms too.
Right the standard is even more vague than I remember. Unfortunately it's the only thing we have.