@christianbundy well, the thing that worries me is the spiraling concerns about who has the right to delete what content. I don't think there is a simple answer. The obvious approach is you can delete your own content - but once your content is on my machine I ought to have some say. It may effect me now - for example, say Alice threatens Bob, waits till Bob sees that, then deletes the message. Or say a politically powerful person deletes a message which causes a scandal - maybe they should be held to record? So peers should have some say whether something is really deleted. On the other hand if anyone can delete anything, what if someone deletes some thing you want, for reasons you do not agree with? Basically, it makes it really complicated, and if you respect everyone's right to have a different opinion on a particular deletion... you end up with something that isn't gonna work very well... and at worst a Streisand Effect button, when someone makes the deleted messages view.

On the other hand, I think removing an entire feed after you've blocked them is straightforward,
and suitable for removing offensive content - remove the whole feed, and refuse to host it, rebuild indexes.

On the other hand, for fixing typos, etc (which I believe will be the majority of the use of deleting a message) I think edit messages will be fine, and don't complicate the protocol.