Idk if it’ll let you edit them without deleting them.

Yup it does, that's how I used it. Did a cycle to edit with random words, afterwards checked if it worked & if it looked okay went ahead with a delete.

The edit feature is to create a new entry on the database in case reddit isn’t actually deleting comments from their database when they show as deleted. Although if they’re doing that then they probably keep a change log of the comments as well.

You know I thought that too. But I've seen some people talk about their GDPR data requests & they received the last edited version of their posts/comments, not the original. The data request doesn't even contain anything like a change log of every post/comment. But I guess you could argue the data request is fulfilled with just the last version regardless of how many versions of the same post/comment actually exists.