This is... unsettling. If this is another way of saying 'no, thank you' then I'd be reassured - but comments below suggest it's not, and that giving 'no thank you' is marked as wrong (since presumably it'd be "Ne, dankon").
But what's the scenario here? Under what circumstances would this - what sounds to me like a desperate appeal for mercy - be used in normal conversation? Is 'No please' or 'Please no' used as an alternative to 'no, thank you' by Esperantists?
(I don't know how old your comment is, it won't tell me on mobile, so this could be eons old, and if that is the case then I apologize!)
There are plenty of times this could be used in regular conversation. It's just "please, no" with some emphasis from the exclamation point. It could be being used sarcastically or for dramatic effect, or it could be being used to express a disagreement about one preforming an action. The action in reference could be anything... A spouse wanting to ask for directions though the other is embarrassed to be perceived as a tourist. A customer being offered service above and beyond what they feel they need and not wanting to waste the time of the employee. Even something like a very young child protesting being put down for a nap, I know I've heard my friend's two year old say "please no!" plenty of times, just because he knows that a) please means he's more likely to get what he wants and b) "no" is his protest word for anything that is happening that he's not entirely happy about.
This sentence could totally mean something dark and creepy. It can definitely be perceived as unsettling. Or, it can be like you said, a way if saying "no, thank you," just with more emphasis (and possibly less politely.) It's all about context :)
I would say that "mi petas" would be more like asking for something, it seems more formal to be(more like i would like), and "bonvolu" more like begging or a casual command/imperative. this is more from context ans general knowledge of romance and other languages than me actually knowing esperanto, i could be wrong.
Shady: I don't understand why you think they should mean the same thing. Mi petas (pronoun verb) translates to I ask, whereas bonvolu ( = please) is an interjection built from the adverb bone (well) and the imperative of the verb voli (wish). Am I missing something?
I'm not being sarcastic; I'm wondering whether I literally missed some lesson that contains information that prompted you to regard these expressions as identical. Thanks, anyone who can fill in the blanks.
According to wiktionary, bonvolu is an interjection.
I don't think it's an imperative, as another user suggested; in English, every verb has a mood (indicative, imperative, or subjunctive), and the imperative is used to issue a command, such as Come here or Stop!