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