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