Jupyter notebooks do support multiple languages. However, sharing objects among the languages is a whole another thing.
If you can find an error in our implementation I would be happy to hear about it (ideally file an issue on github).
I am not an expert in R and I don't expect autotranslation to cover every case, but I think what we have is useful, and I look forward to continuing to improve it based on community feedback.
Thanks, -Scott