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