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