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