Cortex allows you to mention another Cortex user in a comment which will then notify that user.
You can mention users when you're adding a comment when you first create a task, and later on, even after the task is created.
All you have to do is tap the "@" key and then start typing the users name.
When you see the user you want to mention, tap their listing and their name will turn green in the comment.
Then when you save the note, they'll get a notification and a link to open the comment up to review it.