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