Notifications are shown when chat is active and focused
When I'm in a query with someone, with their chat active and Polari as the active application, when they send a message, it'll still display a notification and a "new message" line, which is a bit noisy and unnecessary. I'd argue that when Polari is running in the foreground, there is no need to show notifications.
I'm using Polari 3.32.2-1 on Arch linux with Gnome as my DE.