We got your email and will reply, but as long as the question is here publicly, I suppose the answer should be too.
I finally got to look at this. There's no single pattern with these accounts. For starters, their comments are not all on the same political side. Some are defending Chinese policy and some are criticizing it. I don't see much of a pattern in the provenance of the accounts, either. Some are throwaway accounts being used by established users; in one case it's because we warned them to stop engaging in nationalistic flamewar, in other cases who knows. Some are breaking the guidelines by making a new account for each comment or two that they post. One account has existed for 3 years and the rest are new. To judge by IPs, one is posting from Hong Kong, one from Taiwan, and the rest from North America.
Based on the comments and other data I looked at, my best guess is that these accounts are all people who have spent time in both China and the West. Perhaps some are Westerners of Chinese background while others are from China, Hong Kong, and/or Taiwan and are either working in North America or did so in the past. Most likely they were motivated to create new accounts either because the active discussions going on provoked some reaction in them, or because they don't want their main account to get banned after we warned them, or because they're creating new accounts routinely. Some of their behavior definitely breaks the HN guidelines, but I didn't see anything that suggested more systematic abuse. Nor are they breaking the guidelines in ways that plenty of older users aren't already doing a lot of, unfortunately.
It's always possible, of course, that I missed something important. We don't know what we don't know. But we've spent years working with this data and user behavior and, to judge by the occasions when some real-world verification has been possible, have learned to make reasonably informed guesses.