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