I don't think it's bad karma. I've spent years on Reddit watching other people's TikToks, reading other people's tweets, watching a repost of a repost of a repost of a video ripped from someone's Facebook... If you give them credit, that's more than most people get in the world of social media.
Reddit has a way to embed posts and it would be cool if links to Reddit embedded the content here, but I don't think that's happened yet. If that happens, all you'd need to do is link to someone's post.
I was considering making a bot that automatically cross-posted stuff from Reddit, but it seemed pretty unpopular with the community. The more I think about it, they were right - a bot doing that was a bad idea for this community. I was thinking of setting up another instance with a bunch of communities that had the top posts from their respective subreddits, but I just haven't got the time to figure all that out at the moment.
But I'm going way off track. I think reposting stuff from Reddit is fine.
Edit: @luthis@lemmy.nz - I meant to reply to your comment
I've found that unsubscribing then subscribing again usually fixes it pretty much instantly. But then I was only having the problem on earlier versions of Lemmy so I don't know if that still works.