If anything, shouldn’t it be encouraged, and even automated? I’m including even the ‘old’ stuff from reddit here. Reddit shouldn’t be the absolute owner of the content submitted by users. When I migrated here, it wasn’t because of me being against reddit users, but being against reddit the company. Copying the content here actually hurts the company in sense that they don’t get to then gatekeep the crowdsourced content.
It’s also important to remember too that while the vast majority of Lemmy users by far are Reddit migrants, just because you’ve seen something before doesn’t mean someone else has. Any bit of content can make someone part of the lucky 10000:
https://xkcd.com/1053/