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