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