Generally speaking, when a name is not auto-completed, it's the sure sign that the user will be notified. No need to spell out his name. You don't need to remember "quirks", and how Stack Exchange works, just understand that if a name is not auto-completed, that's because it doesn't need to be.

This is especially useful when you want to address two users at the same time, because Stack Exchange only allows you to mention one with @. So when it comes to picking one of those users, if one of the names is not auto-completed, then you know to pick the other one.

Generally speaking, when a name is not auto-completed, it's the sure sign that the user will be notified. No need to spell out his name. You don't need to remember "quirks", or how Stack Exchange works. Just understand that if a name is not auto-completed, that's because it doesn't need to be.

This is especially useful when you want to address two users at the same time, because Stack Exchange only allows you to mention one with @. So when it comes to picking one of those users, if one of the names is not auto-completed, then you know to pick the other one.