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