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