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