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