Pondian

I think we've previously contemplated some Pondian differences regarding willingness to use "-er" (was it particularly with adjectives ending in what for most AmE speakers would be a rhotic /r/?).

Yes, it is strange which Pondian differences seem to matter most. I'd love to see a theory.

Maybe it's a Pondian thing. That "yes", surrounded by commas, implies a question or doubt in the mind of the speaker.

So I think the real Pondian differences here are other ones: 1) The disappearance (if it ever was established) of the term "greengrocer" from AmE, and its retention in BrE; […]

It is quite curious that the names for items of clothing display so many Pondian differences: trousers, pants, shorts, braces, suspenders, vest, cardigan, sweater, bowler hat, derby hat, etc., etc.