In the rich text editor:
@Pen
In a comment:
[Pen](https://chowlings.com/user/Pen)
For Names and Avatars:
In the rich text editor:
%Pen
In a comment:
[![Pen's Avatar](https://chowlings.com/images/avatars/527.png?v=1644063304)](https://chowlings.com/user/Pen) [Pen](https://chowlings.com/user/Pen)