It seems so miniscule that you take it for granted but once it's taken away and you accidentally walk off a cliff because you forgot to hold down alt to scroll back (NOT THAT I DID THAT) it makes you really wonder how people could possibly have the audacity to be hostile towards addon writers that you so frequently see on addon forums.
Having to hold down alt makes me want to pummel Blizzard's interface designer.
Hope this helps, and hopefully someone better than I can tweak it out so you can select which chat frame you want in on instead of using float to move it to a different one.
Currently the background has a chance to go on top of the font, causing your text to be hard to read in the edit box. Currently can't figure out why or how to fix it.
I used your fix and it worked great, i was finally able to move the edit box to the top. but now whenever i reloadui i get a gap at the bottom of the chat box instead of it being flush with the bottom of the screen, its like it thinks there is an edit box still there.