My uncertainties with the names revolve mostly around the people with a jewish background, since it's a chivalric order for christians.

• Noam Chomsky (born to middle-class Ashkenazi Jewish immigrants)
• Henry Kissinger (was a Jewish refugee who fled the Nazi regime)
• Alan Greenspan (his father, Herbert Greenspan, was of Romanian Jewish descent, and his mother, Rose Goldsmith, was of Hungarian Jewish descent)

But everything is possible. In the names you putted out, those are on both web sites:

• Benito Mussolini
• William F. Buckley Jr.
• Philippe of Belgium
• Queen Elizabeth II (she is at the apex of the Order of Saint John as its Sovereign Head, it is a protestant faction of the catholic Order of Malta, a separate branch much like the old German Protestant Der Johanniterorden)

Some other names I recognized or of interest which are mentionned on Wikipedia's list, and who don't particularly appear as nobility at first sight (prior to the 1990s, all officers of the Order had to be of noble birth (i.e., armigerous for at least a hundred years)):

• Alexander Haig (ex - White House Chief of Staff, U.S. Secretary of State & NATO Supreme Commander)
• William J. Donovan (wartime head of the OSS, the precursor to the CIA)
• William J. Casey (Director of Central Intelligence from 1981 to 1987)
• Pat Buchanan (another important American conservative figure like William F. Buckley Jr.)
• Vince Lombardi (the NFL's Super Bowl trophy is named in his honor)
• Rick Santorum (a U.S. Republican Party presidential nominee in 2012 and 2016)
• Keith O'Brien (a retired Scottish Roman Catholic Cardinal who resigned after allegations he had engaged in inappropriate and predatory sexual conduct with junior priests and student priests)
• Valéry Giscard d'Estaing (President of the French Republic from 1974 until 1981)
• Michael Ancram (letters published in 2012 by Wikileaks show that Ancram was at that time Chairman of Le Cercle, a foreign policy think-tank specialising in international security)