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