Given that we’ve watched communities like Reddit become more closed, I would rather Lemmy not do the same. The best thing an instance can do is keep them on a very tight leash, and kick out at the first sign of a rule being broken.
What Lemmy needs, above anything, is engagement. Be open to the users from Threads, instead of punishing them because you hate Meta. Many people joined Lemmy because the idea of the fediverse meant freedom to choose, and while instances are free to allow/deny who they want, it shouldn’t be a detriment to users that want to experience Lemmy.