I emailed Jeff Bezos about this a couple of months ago. Here was the response they gave me.
I'm Allissa Bratager of Amazon.com's Executive Customer Relations. Jeff Bezos received your e-mail and asked me to respond on his behalf.
I'm so glad to hear you're enjoying your Kindle! It's always gratifying to know when we've succeeded.
I also want to thank you for sharing your thoughts on improving the landscape feature. We really value your input, and are always happy to hear our customers' thoughts on how we can improve the services we offer. To ensure your idea's reviewed, I've shared your suggestions with our Kindle team for their consideration when planning future improvements.
Michael, thanks again for taking the time to provide this feedback to us.
Executive Customer Relations
Here is what I wrote
Someone on the mobileread forums (@ https://www.mobileread.com/forums/showthread.php?t=91752
) suggested I send you an email regarding a feature I really really want.
I am a new owner of your amazing product; the kindle dx graphite. I absolutely LLLLOOOOOVVVVEEEE it, however there seems to be an important feature that it is missing. The missing feature I speak of is the "2 column when in landscape" feature.
You see, the kindle dx is easier to hold when in landscape mode when sitting in a chair, however reading the full length of a line feels "wrong."
It's a small flaw, but I'd really really like it if you could address my concern.
Thank you for reading