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