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