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