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