Amazon does let you list contact information, I don't know why they don't display it on the Appstore pages, but it's there in the portal for us to use when submitting apps. Apple DOES show contact information in the iTunes version of the store, but not in the iOS one.
If you leave a review, there is a chance that a developer will respond if its something they need to address and maybe could test out with you. If a developer sees you around MobileRead and you're complaining, they'll most likely sign up here and address any concerns too. The developer behind PolyClock helped us here when their app wasn't working correctly on the first generation KF.
I usually hunt down developers myself, try to find their website, Twitter handler, etc. They do the same to me, haha. I leave a review on the app store/anywhere on the internet, and they'll find me on Google and e-mail me. One bad review, and it hits them hard.
So yeah, just dig around, you might find their info on the Google Play store, or you may find them elsewhere, like Twitter.