In the rich text editor:
@morgan
In a comment:
[morgan](https://chowlings.com/user/morgan)
For Names and Avatars:
In the rich text editor:
%morgan
In a comment:
[![morgan's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/morgan) [morgan](https://chowlings.com/user/morgan)