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