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