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