Nuking your comments doesn't hurt Reddit or Spez, it just hurts other users who are looking for the answers that you gave. If you want to leave Reddit, it's better to just leave
While as a user it sucks that is exactly the reasons people do it. It takes the value away from reddit, if the content that users want to see it not there people will not go there.
What I find the best compromise is users that take their comments they had on reddit and post them again as it’s own post to lemmy with the context needed. While not perfect the information is at least not lost completely and a google search in the future might actually bring someone to a lemmy instance instead of to a corporation like reddit. But that is obviously a lot of work to do, especially if you have lot of helpful comments on reddit.
If one of their goals is to sell premium access to train LLMs this type of gibberish would hurt that. When you can't guarantee that the data source is coherent, then that would have an impact on the final model that is created.
I think a better approach is to transfer comments to a new platform or create new higher quality content. Could the solution to this problem become a guide that goes into more detail?