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