@cphuntington97 @mokka I cannot speak to Mastodon specifically, but an edit within the existing Fediverse is entirely possible.  You would just need to change the current message to deletion text (what happens in GNU social/postActiv when you delete something anyways), and then set the current message to supercede the old one.  You would just create a new ActivityVerb for this and then have servers respond to it.

This, however, has a few problems:

A: Edits are perceived in general in the Fediverse as undesirable,

B: Even if postActiv or Mastodon supported an edit capability, servers running older versions would not, so it would have to be designed in such a way as to not break federation with older servers (of which there are many, RainbowDash runs original StatusNet for instance)

C: Even if we get past all of that, then you have to address the social issue of people redacting or editing posts to be dishonest.