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