Honestly taking a glance at it it's doing shockingly well for being effectively unmoderated (if the number beside moderation log means what I think it does, there have been no moderator actions, though maybe "admin actions" don't show up there or something).
Open signups aren't novel on the fediverse, lots of places have them. The problem is having them without following up and banning problematic users... but yes I expect that if stricter instance-wide moderation doesn't happen this instance will end up being defederated by most of the fediverse (with mastodon at least that seems to be the norm).
I'm hoping moderation has been been lacking because Ernest is just overwhelmed with the amount of load, and that it is fixed soon, if not I'll end up moving on once admins start defederating it (probably to another kbin instance).
In addition to the more important issues that fedi-tips discusses I find their stance on anti-vax and US-election conspiracy theories... unappealing, which you can see being discussed here: https://lemmy.ml/post/143057
And that they haven't been shy about exerting their power for political purposes. The hardcoded slur-filter was explicitly about discouraging "right wingers" (I put that in quotes because I suspect their definition of right wing and mine differ), and they at least use to be open about their intentions to moderate the instances that they run as explicitly "left wing" (though I don't see a reference to that on the current site).
I can't speak to Lemmy's implementation (I refuse to go near lemmy on account of the maintainers "politics"), but there's nothing fundamental about threading that should make posting slower.
Loading threads here is... different... work than loading your feed in mastodon, it's possibly slower, but posting is from a theoretical standpoint the same. Probably you're just seeing the effect of your lemmy instance not running on sufficient hardware (very understandable given the explosion in user space size).
What is a reddit thread if not a root tweet with a bunch of replies (and replies to the replies) formatted in a way that you see the organization of the replies?
It will change things too, not for reddit, but for competitors (like kbin).
A tiny site can only grow so fast, at some point things start breaking (both technically and as a community) and users stop joining, but as sites grow bigger they also gain the ability to grow faster.
The protest means that every possible alternative to reddit has been growing as fast as it can reasonably support. That's probably not fast enough to hurt reddit this time, but next time it might be.
The real galaxy brain is you, a kbin user, posting a meme about kbin, on a lemmy magazine.