And I'd also prefer if they don't try and hijack other features.
I had installed Messenger, but had notifications turned off because I don't care to be interrupted every time someone sends me a new message when I'm not actively participating in the chat.
Today, someone tried to call me (as in voice call), via the Messenger app. Because notifications were turned off, I didn't realise they had tried to call even though I had the phone with me at the time because it's treated as a 'data' call via Messenger rather than a real phone call.
Given that I can't separate the functionality of 'text chatting' from 'phone calls' made in Messenger, I've now uninstalled it so friends can't pseudo-call me via Messenger.