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