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