Just like tabs vs spaces animosity has largely been ended through the use of auto formatters, I think there is a technological solution as well for this.

Create an auto responder for “Hi” and “Hello” that will just echo it back and not cause a notification.

So it becomes:

Other person: Hi

Auto responder: Hi

(No chat notification)

Other person: <Asks question>

(You get chat notifications, if enabled)

You: Answer question

This seems to solve most of the issues, and should be rather simple to implement.