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