Depends where you are. In the UK, "please could you..." is much more polite than "could you please...", which is quite direct and potentially rude.

like the British thing of reading "thanks so much" or "thanks a lot" at the end of an email as sarcastic.

I think you'll find we're capable of making or reading any phrase as sarcastic :)

Less flippantly (but still true), knowing that there's at least two ways to interpret something and that at least one of them may be humorous helps me remember not to assume bad intent when I hear or read something I don't like. Often it's just their clumsiness or my over-sensitivity.

On the other hand, perhaps it also helps me hear more of the slights that are in there too! You can't win 'em all.