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