It’s up to Lemmy to safeguard that, not the OP.

Uhm, yes? The discussion was never about anything else?

Reddit changes the stuff to [Deleted] or something like that.

I know, and I think that’s preferable. Gives the OP a way to delete their own stuff while not destroying arbitrary amounts of other people’s conversations and arguments.

This is about data posted by other people, though.

Honestly, this is a major weakness of Lemmy. The OP of a thread can destroy a lot of content by other people, and they often do. I really don’t get the reasoning behind allowing them that power.