World was already the biggest by far when I first started lurking back in July, and it’s just getting more dominant. Before, there was quite some diversity in the distribution of generic communities, but nowadays the vast majority of posts that reach the top are from over there.
I really can’t see any specific virtue that it has; uptime is not the best (or so I’ve heard), the moderation is quite lacking (which is demonstrated by the fact that Beehaw defederated them), they make some unpopular moderation choices (like blocking !piracy@lemmy.dbzer0.com), and overall the atmosphere is a lot less… nice than those of smaller instances.
I also feel like it goes against the idea of the Fediverse that one instance has control over most of the platform. Especially on Lemmy, where communities mean that building community within an instance makes so much more sense than elsewhere, and upvotes are federated near perfectly regardless the size of your instance, decentralisation makes a lot of sense. It really just doesn’t make sense to me that Lemmy World is where people are going.
I was not aware Mastodon didn’t actually move the posts, that is quite disappointing.
To be fair, it has a lot of implications. Would your posts be reposted included the likes, reposts, replies, etc? The dependencies among this things can quickly get out of hand, especially in a federated context
Honestly it’s fine. I’ve moved a few times and the first time it was a bit sad, but once you realise it’s like five minutes later and you’re continuing the conversation you were having on your old account with all the same people on your new account the actual historical record suddenly seems a lot less important than the inherent coolness of what just happened :D