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