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