Translation:Can you lend me a pencil?
Since the sentence does not specify that the pencil has to belong to the person being spoken to, 'a pencil' should be accepted and in my experience is equally natural to a native English speaker.
"A pencil" would be common indeed, and I think it's nonetheless implied that it belongs to the listener (which is why the listener has the power to lend it).
agreed. The original Chinese sentence is a little off grammatically to, though it should be fine knowing that corrisponding "一支铅笔" to "a pencil" will probably cause more confusion.
Could you lend me a pencil?
This is correct and translated quite literal. Nowhere in the sentence indicate the pencil belongs to whom/
Sure, effectively, but it's the obverse action, and you should be able to show that you can distinguish the specific Chinese meanings, particularly because "借" can be used for "lend" or "borrow" depending on the structure of the sentence.
"Can you loan me your pencil?" Could/Can loan/lend tomato/to-mah-to; let's go people!
Am I speaking ungrammatical English, or can one also say "Can you loan me your pencil?"
That's fine, though there are some idiomatic differences in using "loan" versus "lend" (and their associated forms) that you can read about here:
I wrote, 'can you lend me a pencil please?' it's wrong. Haha. This app does not recognise manners!
I wrote: "Can I borrow a pencil from you?" This should be accepted. (Chinese as first language but isn't fluent.) 可以 means can I, may I or is it ok if it is a question. 借我 means borrow and 铅笔 means pencil(although I do recommend adding 一个 or 一支) And 吗 is what you put at the end of a sentence if it is a question. Thank you google translate cuz my Chinese suck and I can write Chinese. And this can't copy and paste so I have to find the pinyin.
doulingo doesn't support manners Also, are you Chinese? (Not to be rude but "Wang"- Chinese last name.)