Newt has actually praised Sanctimonium on stage about his foreign policy experience. He never returned the favor or the respect to Newt, his mentor, however. Little things mean a lot...
We agree that little snide slips mean a lot, and often are intentional.
Are you sure that Santorum never returned the favor or respect to Gingrich, or just didn't do so on stage in that particular debate? A pattern over an entire campaign of deliberate omissions carries weight, but we don't necessarily know what they say off-stage or via telephone. My impression is Santorum and Gingrich generally have been civil to each other in public, and Gingrich has reserved his fire for Romney.