In the rich text editor:
@4morant
In a comment:
[4morant](https://chowlings.com/user/4morant)
For Names and Avatars:
In the rich text editor:
%4morant
In a comment:
[![4morant's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/4morant) [4morant](https://chowlings.com/user/4morant)