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