Not having a clue about the derivation and distribution of dialect terms may be ignorant and lazy in the days of Wikipedia , but it's not really a signifier of 'class' or superiority in any direction
Quite so, which is why the op is so ridiculous and why people who do clamour (deny it all you like) to say how they do the upper class thing. Again, not people who have been brought up to say it and that's that, but people who say it because they've been told (by people like the op) that it makes them sound like they come from a more upper class background. Which, whatever way you look at it, is piss your pants funny to my very lower class self (and I'm allowed to say myself in this context, cos I'm Irish).
And gentle mocking of people who say suppah isn't
, don't get your knickers in a twist. I mock my own accent and enjoy the difference between the two. In Ulster, we pronounce our Rs. At the Ulster rugby ground there is a chant which goes:
Give us a U, give us an L, give us an S, give us a T, give us an E, give us an R, give us an R, give us an R, give us an R. What does it spell? Ulsterrrr!
Nobody loses their shit and passes out with offense.
My DH says fathah, as do my kids. I think it's adorable.
When I did a presentation at fancy pants university, I had to say the word fatherrr (in my accent). Everyone giggled and I didn't know why, but later realised it was my accent. It was good natured and I didn't feel the need to clutch my pearls over it.