The notifications won’t be duplicated if it all happens within a single post — this post is a reply, has a quote, and I can mention you @pamelay… and you should only get one notification.
I believe the mention gets priority in this situation when determining what kind of notification this will create, because saying someone’s name is probably a slightly stronger signal than simply responding to what they said.
If I didn’t mention you, you’d get a notification for the reply. And if it wasn’t a reply, you’d get a notification for the quote.