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