You can turn the mentions notifications by going to the list of rooms you follow, then tap on the three vertical dots at the top right of the room tile...
Tap on the room notifications switch to turn off, or turn on mention notifications.
You can also do this in a chat room by tapping on the three vertical dots at the top right of the room screen...
Now tap on 'turn off notifications' to turn mention notifications off.
Please note that you would only see these types of notifications from rooms you follow.