Very good points!

But rationally speaking, if someone who bought the ebook tells the publisher that they would have liked it better if it had feature X, the incentive for the publisher to implement that feature is still pretty low - after all, the guy complaining bought the ebook anyway.

It may have a long time effect though, because the same customer might not be willing to buy the next ebook from the same publisher unless the perceived annoyances go away.

And competition from other publishers might help too.