We can edit comments, how about direct messages?

[neo_skywalker]

Why even make feedback and suggestion forums?

 

[gene.sis]

moderators can access the original version of a message.

Moderators have no way to access any regular conversations they aren't a part of.
(Content moderation conversations created by the moderation panel can be viewed.)

But what could be in a DM that would cause an accusation, legal dispute and security and liability issues?

Well, basically anything that violates the CoC. (That includes rightout illegal actions.)
E.g. if someone starts a conversation "Do you like cute cat images. See this one," and when you click on the link, you're facing a dick pic.

If content is reported, the chapter, comment, or profile (including the most recent comments) is captured.

Why even make feedback and suggestion forums?

I don't think anyone actually objected to the suggestion as long as it can only be done with unread messages.