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