I knew I had seen it elsewhere. It was in Byword. It's possible an iOS bug with dark themes in apps. I thought I had seen it without a dark theme but that's the next thing I must test. At any rate, it's nothing of concern for me. Minimizing the keyboard and bringing it back up seems to fix it for the time being. I seem to get it even just from home button exit and return through icon on home screen. Here it is in Byword though.
Please test the updated version on an iPad with the split keyboard enabled, both docked and undocked and split and unsplit. The current release keyboard bar is broken in various ways when split mode is enabled including:
Sometimes the extra row overlaps with the normal keyboard.
When the extra row is positioned properly, the buttons don't work. Instead, the touch events fall through to the piece of the document the buttons cover.
Yes, I have URL escaping enabled, and have tried both escaping in the x-callback action directly and with using the separate URL escaping action. As minnepicker described, using both works but isn't really helpful :)