Ability to deprecate channels, i.e. have them visible for reference but do not allow new messages.
This would help with consolidating channels (as an alternative to merge channels) by positing a "this channels is closed" please go to channel xyz .
Jesper Sommer commented
There is already a request for archiving channels; it has over 4K votes :-)
Ben Williams commented
I agree. An option to "archive" a channel would be excellent