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