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