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