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