Hrmm... Textastic is a sandboxed app and uses the standard NSDocument mechanisms. The Open panel and iCloud are completely handled by the operating system. Because Textastic is sandboxed, it has no access whatsoever to the open panel.

So I think that's probably something that needs to be fixed in Default Folder X.

Does this problem also happen in other apps like Apple's TextEdit?

You can just drag the file icon from Textastic's window title bar onto the other editor's dock icon. This will open the file in the other app while it is still open in Textastic.

In iOS 8 it will be possible for developers to create system-wide custom keyboards and distribute it through the App Store. I'm pretty sure someone will develop a Dvorak keyboard.

Sorry, but I don't plan to add more localizations at the moment.

Are you sure you are in the right support forum? This one is for the app "Textastic" which is only available for iOS and Mac. 

Can you reproduce it reliably?

This should already be the case.

I slightly changed the undo behavior in Textastic 3.0 which is currently waiting for review at Apple and should be available on the Mac App Store in a few days. Please let me know if the new version still has this problem once it is released.

I added it to version 3.0 of Textastic for Mac (currently waiting for review at Apple) and plan to add it to the iOS version.