I would argue that if you have any posts/comments with very helpful/popular content, repost it in Lemmy, then edit the Reddit post/comment to point to your Lemmy copy.
It won't work for everything that you've posted/commented, but if you pick out the biggest things it will help bring additional content to Lemmy, and hopefully some more users as well.
I think users have also been uploading massive files of white noise to Reddit... Louis Rossmann spoke about this during a recent video:
https://odysee.com/@rossmanngroup:a/reddit-ceo-learns-going-to-war-with-the:9?t=87