In the rich text editor:
@Ly0nz
In a comment:
[Ly0nz](https://chowlings.com/user/Ly0nz)
For Names and Avatars:
In the rich text editor:
%Ly0nz
In a comment:
[![Ly0nz's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/Ly0nz) [Ly0nz](https://chowlings.com/user/Ly0nz)