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