Los Angelas to Hong Kong to Shanghai to Los Angelas

Dave, if so, you can enjoy the 144 hour free transit in Shanghai. Nice trip!

Doesn't look like it, Dave. I asked same sort of question Auckland-Guangzhou-Shanghai-Guangzhou-Auckland, and apparently people are saying I need a visa.

That's because you are not in transit. In David's case he is doing HK-Mainland China-US. You are doing NZ-Mainland China-NZ. David's trip is fine while yours is not.

paulinei, you need a visa because New Zealand-China-New Zealand is not a transit. If Dave flies Hong Kong-China-USA that is a transit and qualifies for transit without visa. Only the flights immediately before and immediately after China are relevant. If Dave flies USA-Hong Kong-China-Hong Kong-USA then he does need a visa.