Slack/Facebook comments/posts are all things I use that let me delete previously sent messages. This is possible because they control it all. (Of course, I'm re

Slack/Facebook comments/posts are all things I use that let me delete previously sent messages. This is possible because they control it all. (Of course, I'm relying on the other users' clients coming online and respecting the delete instructions) and fair points about email... I had assumed this worked like other parts of Facebook, which doesn't seem unreasonable given they control the whole stack. (and they did shut down their old XMPP gateway awhile back)