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