In the rich text editor:
@mario
In a comment:
[mario](https://chowlings.com/user/mario)
For Names and Avatars:
In the rich text editor:
%mario
In a comment:
[![mario's Avatar](https://chowlings.com/images/avatars/857.png?v=1644063335)](https://chowlings.com/user/mario) [mario](https://chowlings.com/user/mario)