If it's against the rules, like a meaning change rather than a correction, you can report it. I don't see how simply leaving your name next to it and leaving the site helps anyone nor lets the person who did it even know they made a mistake (without link, from experience moderating the edit queue I can only assume good faith by default since the overwhelming majority of the edits I reject are made for understandable reasons; one of my reject reasons is conflicting with the author's intent btw, and there's no qualification about the author needing to be correct)
Edit: I'm not sure this needs a disclaimer at all since I'm a normal user but, to be clear, I have no affiliation with Stackexchange. I posted answers mainly on the IT security site and one of them blew up the karma points, giving me access to some of the moderation queues on that specific site. I was always annoyed how slow these things are handled so I started looking at those queues on occasion, and that's basically all moderation I've ever done. No special instructions from, communications with, or particular love for the company that operates the site. I just feel that the parent comment misconstrues how the software works if it wasn't actually the company that made the edit in a hidden way (I only know of that happening for things like switching http to https)
The idea is supposed to be that you've been on the site long enough to learn what a valid edit is by the time you get access to those queues, and it's tested by having already-handled edits mixed in to your queue. IIRC if you get it wrong it tells you what you should have done.
Delete - yes, if it's not the accepted answer or locked. But deleting highly-upvoted answers is generally discouraged.
Edit - Probably not. Editing to correct it might be possible if it's not locked but editing to add such a disclaimer would be problematic.
The best course of action would be to request disassociation, so that it's not attributed to them any more.
I've made drastic edits in the past... but the goal was always to capture the intent of the writer. From your anger it sounds like someone, a mod, went way beyond that?
Right. Editing a message should be for stuff like typos, markup, bugs in example code, etc.