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