So, they allow changing your handle to a random string, they delete selected posts if they don't break big threads, and they redact select info (like PII) from your posts, all of which upon request, and on a case-by-case basis.

To me, it seems reasonable enough actually, although the process could have less friction, i.e., instead of requiring an email conversation, just have buttons for edit/delete after their window has passed that the mods then review and get back to you for further clarifications or simply allow your edit/delete request.