In the rich text editor:
@ferret
In a comment:
[ferret](https://chowlings.com/user/ferret)
For Names and Avatars:
In the rich text editor:
%ferret
In a comment:
[![ferret's Avatar](https://chowlings.com/images/avatars/689.png?v=1644063320)](https://chowlings.com/user/ferret) [ferret](https://chowlings.com/user/ferret)