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