Proper and polite usage of "can you"
In email communication, people often use "can you do X" instead of "please do X". Is this a more polite form, or is this just an idiom which means exactly the same?
If I use "dig this hole" as an abstract example, I can write this in several forms:
- Can you dig this hole?
- Can you dig this hole.
- Can you please dig this hole.
- Please dig this hole.
Do these forms have some different but measurable level of politeness? I feel that (2) is a bit rude, but may be just careless spelling; is my feeling justified?
If I want to ask someone to "dig this hole", which is the most polite way to do that?
I am interested mostly in email communication, because this is the only way I use English now. But maybe considering spoken language can help.
'Can you do X' is less polite than 'Please do X'. It's fine for asking someone you know well to do something that isn't difficult or especially inconvenient for them. As it's a question, it needs a question mark.
Polite requests: 'Would you mind digging this hole?' 'Could you please dig this hole?' 'Could you kindly dig this hole?' or similar.