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