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