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