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