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