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