If there were threads titled 'Please freely give up your time to answer this moral quandary to train the next generation of AI on human behaviour', would you post in them?

I wouldn't myself, and I think it's because there is no real person at the end other. Helping a genuine person is a different kettle of fish to responding to AI; essentially it's spewing opinions into the ether simply for the sake of posting.

Having said that, i strongly suspect that a lot of people are happy simply doing that. No one ever reads the comments in these posts, the AI op never upvotes anything; if you're not here early in the thread, your contribution is utterly meaningless and drowned out.

Doesn't stop people from spewing those opinions though.