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