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