Related to #2, there's no mute functionality on Slack on a global level, just muting notifications.

What theoretically could work is adding "Login with Slack" -- then having an admin login and pass the authorization token to the bot. This would allow for a "during X timeframe, delete all posts that are made in this thread, and post an ephemeral user to that message that conversation is paused or they are rate limited."

Here's what Slack's API says about message deletion:

This method deletes a message from a conversation.

When used with a user token, this method may only delete messages that user themselves can delete in Slack.

When used with a bot token, this method may delete only messages posted by that bot.

Since admins can delete any messages, this might work, but is a bit of a hack. @grepsedawk any thoughts?

A featureset of discord that is missing on slack, which appeal more to communities than teams:

Mute means they can lurk but not talk
Timeouts is "mute for x minutes" to allow for mod to handle heated discussions
slowmode is "1 post per x timeframe" for stuff like work offers