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