Speaking for myself (an American), when I read published work that uses British spellings and I know the author is American, it feels to me that the author thinks American spellings are somehow vulgar or improper and he/she is trying to rise above our shameful misspellings.

British Commonwealth authors (well, really any author I know to be not from the USA) get a pass because these are the spellings they were taught. Nothing wrong with that.

This is a phenomenon I've only noticed in the last two decades or so. I don't know if American students are now being (wrongly) taught British spellings in school or they merely think their writing will carry more weight if it has a British "accent" but it just seems arrogant to me.

The OED is a useful resource but it is not our dictionary of final arbitration. Americans should use the American Heritage Dictionary.