Translation:Please say it one more time.
another translation can be: "Please, say it again" or "Repeat, please"
Yes, another translation can be "Please, say it again," but no, "repeat, please" is not a good translation.
If "one more time" is 再一次, can someone explain why "please say it one more time" isn't: 请说再一次?
This happens because 再 comes before the verb to mean "... again", and 一次 makes this more specific by saying it should happen once. Combined this becomes "once again", i.e. "one more time". So only in translation without context you get 再一次 as one unit.
Can the word 'time' in "一次" (one+time) be used for the concept of time more generally, or is it one of those classifiers? (And I only know classifiers seem to follow numbers etc. sometimes, but not much beyond that - the whys, whens and such are lost on me at this time.)
次 just means "instance, time, etc.", so yes, you can use it to describe the number of times something has happened.
I am not a native English speaker. Is something wrong with my variant "Please, say this one more time."? It wasn't accepted. Not sure if I should report it.
"Please, say this one more time" is not very common. The more common phrase is "Please say it again."
If you use definitions, "this" and "that" just seem like opposites. But the way we use them, "it" and "that" can be more general, and "this" feels more specific. That's in English.
In Duolingo, it is teaching you specific words at this level, and it probably doesn't want you to use "this" or "that" because those are 这 and 那.
I'm not a native Mandarin speaker, but it also seems like 这 and 那 are less flexible, and the "it" is often implied.
Even if you said this, you would be understood, but it would not sound like a native english speaker because of the sentence structure
In class we learned 请再说一遍. Can someone explain how this is different or which one is more commonly used?
In English you need an object with the word "say." It's a transitive verb and must take an object.
That's a really long and drawn out explanation, but you can report it if you would like for it to be accepted.
The more literal a translation is, the more likely it is to be accepted.
I think it is because in English, you only need 'again' OR 'one more time'. Using both is tautological, meaning one of the words is superfluous; it does not provide any additional information.
One could use that tautology for added emphasis in some situations, but normally, one would not do so.
"Can you please repeat that" was wrong, but "can you please repeat that again" is right.
"Please say that again" or "Please say that one more time" sounds far more natural than using "it" here.