The change as a function of the site owner's decision, however, would hopefully have a chilling effect on people's need for social reinforcement in the form of like chasing, and the associated cases of suicide that have happened as a result of not getting that reinforcement.

I suspect that's where instagram is aiming, and they probably see a point nearing where that'll be forced on them by european government(s) attempting to reduce the amount of high profile 'social media' suicide.

An optional opt-in system like your implementation is great, but sadly doesn't tackle that problem.