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