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