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