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