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