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