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