If I follow you, Harry, there are truly no differences between tune settings, style or ornamentation that can be characterized, generally speaking, as regional… All of us who hear regional styles, give or take exceptions, are mistaken.
Of course, it follows that there are no regional differences, then, between Irish fiddle playing and, say, Bretton, Canadian or Appalachian, since many players now mix and match, exposed, as it were, to the other musical ideas or idioms. That there is no appreciable, discernable difference between Irish band fifing and American. Blues has regional descriptors - Chicago, Delta, Texas, etc., but perhaps that’s just wishful thinking on the part of, well, everybody.
O’Neills, for the record, was compiled in Chicago by an extremely small group of players who played together regularly. The settings there are surely regional.
Or is onlyIrish flute playing that is a musical anomaly, incapable of ever being identified by local taste and style, by regionally preferred rhythms, speed, and general character? I hear differences in playing styles from city to city - even pub to pub - here in the US, based on local tune choices, revered players copied, even what instruments or makers are preferred. Those who learned their craft from, predominantly, CDs, still chose who to listen to and copy styles based on a preference for a kind of style - simple and elegant, highly ornamented and improvisational, honking or buzzy or sweet and haunting. If I flip through my preferred players’ list, I find that they share a great deal in common; many, but not all, fall into a general regional sound or approach. Without having spent a day in Ireland, I did spend uncountable hours playing along with, and learning tunes from, very specific players, most of whom came from a one county in Ireland.
I do believe it become meaningless - nit-picking, really - if we analyse style too much, establish hard and fast rules to regional styles, and cast one player or another in or out based on his/her individual musical choices. But to say that there never are, and never were, regional preferences for style, settings, tune choices and execution is equally meaningless.
BTW - I greatly respect and admire your playing, Harry, and even see your point(s) on this. I get and completely agree with the “on the ground” thing; I doubt anyone seriously and deliberately learns to play with regional in mind. So we could, of course, just not discuss it - agree to disagree - without disparaging comments about internet folks who speak on topics without knowing what they’re talking about.
But then C&F would become a very quiet place.
(… in this case tho it very much seems as if the wood is often not actually made from real trees!)