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