Not only that, these presumably would all be old posts/comments being re-posted with current date/time. Maybe best to make sure the specific community or instance you're sending this to accepts old Reddit content.

Interestingly this could be a use-case for Lemmy users having their own self named communities where they can dump old post/comment data into if they wish. e.g. for you it would be https://sopuli.xyz/c/MentalEdge (if it had existed).