politeness - How much more polite does the word "please" make a request?

When I learnt "could you possibly" pattern, my friend said to me this is very polite form to use when I make a request.I said 'how about if I use the please also with it" and he said ' it is a bit too polite that almost in a begging manner'. I can understand that but what I would like to ask that there are other ways of making request.For example :

Would you open the window

or

Could you open the window

But in these forms it is ok if I do not use the word please?

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Does its politeness degree change depending on where to use the please?

For example :

Could you please open the window

or

Could you open the window please?

Which one is more idiomatic or more polite ?

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And at last but not least which one is more polite?

1. "Would you please open the window"


2. "Could you please open the window"


3. "Could you possibly open the window"


4. "Could you possibly open the window please"



5. "Would you mind opening the window"


6. "Would you mind opening the window please"

Answer

I agree with your friend that if you use please in addition to another "softening" phrase in your request that it could be perceived as somewhat obsequious or even a bit sarcastic.

As Adam mentioned, inflection is very important. These examples could be spoken in a way that makes them more of a demand than a polite request.

Could you possibly roll down the car window please? The next time you decide to eat 5 bean burritos for lunch, you should drive by yourself back to the office.

Would you mind taking your feet off of my desk, please?

I tend to use "Could you..." mostly if there is some doubt as to whether the person is able to do what I ask. I think it's fairly common in AmE to make that distinction, but I'm certain some folks don't see much difference between "could you" and "would you", so it's not really a rule that you have to follow.

Could you possibly speed up the process for me? I need to get those permits before next week.
Could you please speed up the process for me? I need to get those permits before next week.

I tend to use "Would you..." mostly in situations where I'm asking the person if they would be willing to do what I'm requesting.

Would you help me carry these boxes please?
Would you mind helping me with these boxes?