In the rich text editor:
@Scragster
In a comment:
[Scragster](https://chowlings.com/user/Scragster)
For Names and Avatars:
In the rich text editor:
%Scragster
In a comment:
[](https://chowlings.com/user/Scragster) [Scragster](https://chowlings.com/user/Scragster)