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