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