What is the difference between these two phrases:
Can you please do this?
Can you do this please?
Is the latter one (putting an extra emphasis on please), considered to be a less polite and a more direct form?
There is absolutely no difference between them with regard to politeness. English is just not that sensitive to politeness: we don't have the finely-striated levels of politeness of, say, Japanese. Context and tone of voice can change any of them from a very polite request to a direct order with a veneer of politeness.
There is a slight difference in meaning, or at least emphasis. "Can you please do this" emphasizes the request, while "Can you do this please" emphasizes the task: the former asks you to do something, but what that something is is not that important. The latter asks you to do this, not that. However, this difference is very, very slight. And again, context and tone of voice can drastically change the interpretation.