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