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