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