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