In the rich text editor:
@Hack
In a comment:
[Hack](https://www.whistlercrest.com/user/Hack)
For Names and Avatars:
In the rich text editor:
%Hack
In a comment:
[](https://www.whistlercrest.com/user/Hack) [Hack](https://www.whistlercrest.com/user/Hack)