Just FYI, not (at least solely) an Italian engineering touch; Yamahas as far back as my 1972 DS-7 250 have had reverse thread mirror bosses on the left mirror, so that wind pressure on the mirror is tightening it, just as wind pressure on the right mirror on a conventional threaded mirror stalk is tightening it.
isn't it the other way round? The right mirror loosens when turned clockwise? My thoughts were it's so when you hit the dirt your mirror will spin instead of snapping off. Pretty sure my old 70's yammy had the same deal.
Then again I am in the southern hemisphere, so maybe our bikes were delivered the opposite way, something to do with us driving on the "wrong"side of the road or maybe ....the coriolis effect.