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