It seems simliar to how reddit handles it where the comments just get a flag attached to them and the text is still stored. There was some hubbaloo about it a few years ago where people were saying to edit your comments first on reddit before deleting them
Yeah, that's what it's looking like. It's a bit concerning because the Lemmy devs didn't have to do it that way. They could just mark content as deleted and then zero-out all the fields to default values. I wonder what their reasoning was for not doing it that way.