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