In the rich text editor:
@Mitts
In a comment:
[Mitts](https://www.worldofgaia.org/user/Mitts)
For Names and Avatars:
In the rich text editor:
%Mitts
In a comment:
[](https://www.worldofgaia.org/user/Mitts) [Mitts](https://www.worldofgaia.org/user/Mitts)