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