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