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