Unfortunately, that doesn't work. The result is the same as Patsy describes. I'm one of those "middle name users," and after previous experimentation I can attest that Ros and Melanie are correct in their comments. In order not to appear as "Edison E. Williams"--because then I'd feel an undeniable urge to remove all capital letters a la e.e. cummings --I have to leave the middle name field blank. Without an underlying code change by WikiTree, there's no way around it.
Edited to add: Might also be worth seeing this previous G2G discussion. The name display operations differ somewhat based upon the privacy level of the profile. For active member profiles set at "Private with Public Biography and Family Tree" or lower, there is no possibility of adding anything in the middle name field without it displaying as an initial. Also interestingly, with that level of privacy, the "Name Displays" menu option does not show what is actually displayed on the public-facing profile; i.e., in no configuration does the "Name Displays" function show my public-facing profile as "Edison E. Williams," which is absolutely what displays if I have anything in the middle name field.
I never considered it an urgent matter, but it does occur to me now that if get hit by a bus this afternoon, someone would have to piece together my real name from my newly-opened profile that has no middle name.
So, a retraction: I believe the name can be set to display properly if the profile is set as either Open or Public, but cannot if it is "Private with Public Biography and Family Tree" or any level more restrictive. Patsy's profile for Vernon Greer is set to "Private with Public Biography and Family Tree," so Vernon's profile has the same problem as mine when it comes to that pesky middle initial.