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