language play--not getting it

It's come up before on this blog that it sometimes happens that people will see an error or non-standardism in English, spoken or written by a speaker of another dialect, and assume that that way of saying/writing is standard in the other dialect. It's a shame, though, when such 'errors' are intentionally non-standard, because then the assumption that it's "just a different dialect" leads the assumer to miss some nuance of the communication. For instance, sometimes I'll say to Better Half, Ya done good. By putting it into a non-standard dialect (and not a dialect that I speak), I'm trying to add a bit of light-hearted affection to the compliment--something that's not communicated by You did well. Better Half knows enough about AmE to get this, but if I said it to a student, they might assume that that's part of the standard dialect that I usually speak and not get that I was trying to build rapport.

Anyhow, a nice example of this 'assuming it's standard' behavio(u)r came up on recently on the (AmE) copy-/(BrE)sub-editors' blog The Engine Room. There, blogger JD admitted to having believed until recently that Americans spell cemetery "sematary" because of the spelling in the title of the Stephen King book, Pet Sematary. In the book, one is supposed to understand that it's misspelt because children wrote the "cemetery's" sign.

That reminds me of being informed by BrE speakers that "thru is the American spelling of through". No, it's not. It's an abbreviated spelling form that is used mainly on signs (or painted on a road surface), and thus it's become the typical way of spelling it in drive-thru. You won't see thru replacing through in American newspaper articles (though it might be handy for an occasional headline--but I cannot recall seeing it in any) or novels--and you'd better not use it in essays for school/college/university.

Do you have any stories of misunderstood intentions due to "it must be the way they say it in American/British English" assumptions?