I don't think that mixing UK/US usage is a hanging offense. In many cases, the author simply may not realize that "flat" is a UK term while "apartment" is the US term.
If the story is otherwise good and worth reading, I would be inclined to send a feedback note praising the story and pointing out that oh, by the way, Character X (an American) would use the word "apartment" instead of "flat."
Getting character's voices true is very difficult-- I know, for example, that my Spike suffers because he gets more like my voice and less like his own show voice. And I also know (another example from this fic) that the Draco in my head would never say "off of"-- it's entirely too plebian-- but this author thinks differently.
Huh. Well, the fact is, language moves and changes. I don't use jumper to mean sweater, but I would use flat to mean apartment (and do). Unless it's actually confusing or really stands out (as with a man in a pregnant-looking dress), I shouldn't think it's that big an issue.
Or, I suppose, there's an absolute threshold below which dialect and variant vocabulary are not noticeable to me, and then above that threshold it's a game of "cosmopolitan, ignorant, or trying too hard?"
Whereas more than 2-3 words in a foreign language automatically qualify as "trying too hard", for me, and that goes double on TV, and that goes triple when the TV actors don't actually speak that language. (Bad Firefly! Alias gets a pass only because (a) Vaughn is French and (b) they sometimes use subtitles.) Foreign words with translation -- trying too hard but at least concerned about the reader; foreign words without translation -- probably the author is being snotty. Heaven knows, I have been snotty, but that does nto stop me from hating it in other people.
I shouldn't think it's that big an issue.
'Scuse me for being way OT, but I just really need to kiss Nutty's feet here. Not "that big of an issue." No, precious, "that big an issue." Thank you!
So the Brits say "mobile" instead of "cell phone"? This is important because Ethan is yelling at Giles for not having modern communications equipment.
Yeah...but you might want that confirmed by actual UKers...so I'll just find an elsewhere to be.
I bet all the UKers are in bed by now. Piffle, I want to finish this tonight.
What would be the search string?
And now I'm channelling Michael Jackson
"Just Google it! Google it!"