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