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