What I meant by registers was different relationships/pronouns/verb endings to indicate different levels of politeness. I should have written honorifics. Japanese and Korean have these. Chinese languages don't.

I thought of mentioning tones, but they're not as much of a problem for learners as they're made out to be. Cantonese has seven tones. However, there are no word pairs where the only difference is that one has a high level tone where the other has a high falling tone.