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