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