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