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