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