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