In the rich text editor:
@Kryonix
In a comment:
[Kryonix](https://chowlings.com/user/Kryonix)
For Names and Avatars:
In the rich text editor:
%Kryonix
In a comment:
[](https://chowlings.com/user/Kryonix) [Kryonix](https://chowlings.com/user/Kryonix)