Learn English – How to ask a question politely

Repeating my answer to this related question, I searched Shakespeare's plays, and found these two examples where it appears that can and may are used in ways opposite the commonly prescribed can we/may we distinction. I don't know when or how this distinction developed or was prescribed, but my conclusion is that it is not a historical feature of English grammar.

From Shakespeare, Cymbeline, Act I, Scene 4:

Can we, with manners, ask what was the difference?

From Shakespeare, All's Well that Ends Well, Act I, Scene 1:

Ay. You have some stain of soldier in you: let me ask you a question. Man is enemy to virginity; how may we barricado it against him?

I think the problem may be that unlike, say, German (which has dürfen) English doesn't have a modal verb which always means "to be allowed to". For example, if I say "It may be rainy tomorrow," I do not mean that I am permitting the clouds to rain. The modal verbs can and may have both been appropriated for this meaning in English, but I don't see any clear semantic reason for using one rather than the other. Without either a semantic reason for or a historical tradition of making this distinction, prescriptive grammarians are fighting an uphill battle.

"Thanks, no harm done," suggests that you acknowledge the grievance but that it wasn't significant enough to distract you until the apology, along with the recognition that the apology was both due and duly acknowledged, tying up the loose ends nicely. :-)