The case: large group with 500+ members, and often someone has to notify everyone in the chat about something very important and urgent. Separate chat is not a good soultion: people will discuss notifications right in that chat, which leads to floooding the chat. As a result, the initial message is lost, and users have notifications disabled for that group.
So, the setup is: a chat, a channel and bot with admin privelegies in both.
When anyone replies to the message with
! sign, that message
is forwarded to the channel. That’s it.
Very specific case, perhaps.