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