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