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