I just posted a review on Amazon using the stock browser, and Super Keyboard. It was 14 lines of text, so I copied it and pasted it in again at the bottom of the text to make it 28 lines. But I did not have any problems at all navigating the window with the touch screen, so I'm not sure what it is you are seeing.
Edit... In the "seller" reviews, where you are only allowed 400 characters, the stock browser doesn't display the scroll slider that the review field shows on a PC browser like Firefox. But after over-filling that review field, I was able to scroll up and down in the tiny field with a carefully placed fingertip. However, the arrow keys on SuperKeyboard also allowed me to navigate around in that field and remove the overflow.