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