- Please may I have the napkin?
- May please I have the napkin?
- May I please have the napkin?
- May I have please the napkin?
- May I have the please napkin?
- May I have the napkin please?

There are six possible ways to place the “please” in the question above. #1, #3, and #6 make grammatical sense. In fact, they mean precisely the same thing and convey the exact same information.

#4 is ok, but sounds stilted.

#2 and #5 are completely unacceptable ways to ask the question (unless, for instance, the napkin has the word “please” on it, in which case you could use #5 but the meaning would be quite different from the rest).

So the questions I have are why is it acceptable or what purpose does it serve to have 3 ways of saying exactly the same thing using exactly the same words? And given that you can combine it appropriately 3 different ways, why is it inappropriate to ask the question in the other 3 ways?