"Can I get one plate?"
Yes, super common kanji, reported because it's still not accepted as of (2.16.2018).
COUNTER の NOUN PARTICLE VERB
NOUN PARTICLE COUNTER VERB
If you find you have a particle between your counter and your verb, you're probably wrong 99% of the time. (COUNTER PARTICLE VERB)
I'm confused. It accepted the をafter the counter in the sentence with chopstick counters. But this time before?
を should always come before the counter when used in this way. Not sure why it would have been accepted with the other counter (which counter were they using for chopsticks by the way? Was it ほん? Because there are several ways to count chopsticks...)