well, go first to the artist profile, you can find it on the upper left side: Home > Entire collection > "artist name" click on it!.. once you are in the profile go to "display" there you'll find the primary name and the sort name... if you put "Jackson, Michael" as the sort name, then it will appear just like that on the left tree, now if you put Michael Jackson as the primary name, then it will appear Michael Jackson on the left tree...

Hope this will be useful!