"kita makan pisang dengan cokelat dan kacang" was marked wrong, suggesting to use "Kami" for "we". Is formality important here?
I don't think think there's a difference in formality. Unless I'm mistaken, "kita" is "we" including the person you're talking to, and "kami" is "we" but not including the person you're talking to. I think both should be accepted.
What are the thoughts on accepting informal speech? I would always use 'sama' instead of 'dengan' to mean 'with' when I speak Indonesian, but it's being marked wrong.
Yeah I did the same.
Should the variant spelling "coklat" also be accepted?
I see it spelled "coklat" just as often