I haven't used FB Messenger, but I also hate features where they show if the other person is typing a response. I intentionally disable it in Slack, so the other person simply sees a response when I'm done with it.
FYI, I don't think that is possible in Slack. You can choose to hide typing indicators in your view, but AFAICT you can't prevent other people from seeing when YOU are typing: https://twitter.com/SlackHQ/status/1057288342671368194
I guess someone like me could make a browser add-on, too. Though I don't know how many people use the browser client vs. the app.
If you run a proxy you could also block those requests.
Likely against their ToS (https://old.reddit.com/r/programming/comments/9bc6gi/bye_bye...)
I had a 3rd party client (aMSN) that would popup a chat window as soon as someone would start typing an initial message to me. I would say "Hi" to them first and they would thing it was a big coincidence that they were trying to talk to me at the same time.
They kept incrementing the server protocol version without updating the client. Eventually all the clients just stopped being able to connect. Strangely, for a long time, only the version bundled with XP stayed working, until eventually it too could no longer connect.
> Hi
(waiting) (waiting) (waiting)
< OK Hi
(typing) (pause) (typing) (pause) (typing) (pause) (typing) (pause)
FFS hurry up already