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