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