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