From what I read, this also breaks sponsorblock - as the ads are part of the video, it moves the time stamps of the video so it makes it not correct. The ads will also change I imagine so idk if sponsorblock will be a solution.
So that the timestamp adjustment can be propagated via uploader or user comments across YouTube clients on all platforms... i.e. to avoid having to hardcode each adjustment for each ad on each video on every client
Why couldn't they just serve the comments to each client with the ad-adjusted timestamps already? The only thing the client has to request then is the comment page it wants to load, and some unique ID for which the backend remembers which ad version it's associated with.
No, not in it's actual form, nor the front-ends can't not longer cutting the ads with their current form. Or they change their script, or you have the alternative to use YT or using another streaming service. But I think that there will be other solution in the future to show the middle finger to YT.