For example, once officially sanctioned in manufacturer windshield service documents, feldspar-powder containing Bon Ami 1886 Formula Cleaning Powder now cautions for "vintage auto windshields (not modern windshields, which often have coatings)" - these sorts of glass warnings, also noted with lesser Mohs-scale abrasives, surprised me as I only imagined something rare like a projected heads-up display might call for any coating, and that presumably only on the interior.
(The question originally arose from an investigation into cleaning methods for interior windshield fog/films resistant to everyday spray-and-wipe cleaning. Likely a build-up of plasticizers outgassed from interior plastics, the very-minimal published science implicates urethanes as the principal source. Online car-care advice for this problem varied except in that virtually all include an initial abrasive step, presumably to physically break-up the film before removal with a traditional cleaner and microfiber cloth.)
