In the rich text editor:
@ScribbleTheCat
In a comment:
[ScribbleTheCat](https://chowlings.com/user/ScribbleTheCat)
For Names and Avatars:
In the rich text editor:
%ScribbleTheCat
In a comment:
[](https://chowlings.com/user/ScribbleTheCat) [ScribbleTheCat](https://chowlings.com/user/ScribbleTheCat)