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