Translation:Please arrive earlier.
I think the Chinese phrase is trying to reflect a situation in which you are asking someone to arrive earlier than they normally would or usually do; in that case "please arrive a little early" wouldn't work.
I disagree. To me "please arrive a little early" can exactly fit the situation you describe. In fact it does so much more clearly than the version with "earlier".
Maybe @MelvinBret and I didn't express it clearly enough. I (We?) meant “normally, usually”, AND specifically for this simple imperative sentence in Chinese. (Now I'm not arguing about the Duolingo's acceptance of the translation, and I should not say “should not” in my previous comment. ;-)
I can imagine a situation that “a little early/earlier” is the exact translation but the most usual interpretation is just “early/earlier” for this sentence. Literal translation is not always the best.
You may think 一点儿 is here to soften the tone, but at the same time nobody can think of a shorter sentence. For example, 请早到 is too short and sounds abrupt, thus it is not good enough in most cases. 请提早到 sounds rather specific, so it is also not preferred for a general request.
Yes, 一点(儿) should not be translated here. Why should we care that little bit of time? If we really care about that, we should give the exact time, e.g. 请早五分钟到 (Please arrive five minutes earlier.)
Isn't it please come earlier has the same meaning as please arrive earlier? The system considered my answer to this phrase to be false.
Why not also "Please arrive a bit early"? For instance, advising somebody to be at a station etc a little before departure time.
Does this necessarily distinguish between "here" and "there"? For example, could it be telling someone to "please get there a little earlier?"
Here 到 just means "arrive"/"go to" some understood location, so yes it could be "here" or "there".
a question to native english speakers: can you use sooner instead of earlier in this sentence?
Yes. It is personal preference. I have said it both ways. However, for Duolingo you should use 'earlier' since the character 早 means: early & morning. Maybe they will accept 'sooner' in the future.
Is 儿 a requirement in this structure? Previous lessons said it is not required.
"Please be there a bit early" feels a good bit more natural for my English -- though for me, "be there" doesn't really need to be referring to a specific "there" (i.e., the sort for which 那里 might be used), but I do realize that the ambiguity may be best just avoided...
But I figured it worth mentioning nevertheless, in the interest of discussion.