In the rich text editor:
@sir_basil0
In a comment:
[sir_basil0](https://chowlings.com/user/sir_basil0)
For Names and Avatars:
In the rich text editor:
%sir_basil0
In a comment:
[](https://chowlings.com/user/sir_basil0) [sir_basil0](https://chowlings.com/user/sir_basil0)