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