QA came back and found a problem with the functionality of CKEditor under IE8/9/10/11. Basically there are some drop downs within the primary toolbar that are misbehaving. Under Firefox the drop downs (which produce an iframe displaying the drop down content) were not displaying the second time, which is why I was applying the _moveToTop fix above, however there is apparently a similar problem under IE where the drop downs display properly, but immediately disappear after displaying.
I rolled back to 1.9.x and sure enough the problem doesn't exist there - so it's likely related to the same issues that were affecting other parts of the tool.
The good news is that this appears to be the last issue that needs resolution for me to attempt a production release. The bad news is that I have literally no idea how this display/hide event is occurring.
I'm a little surprised to be hearing about this now, as I can find no-one else complaining about this specific problem. Maybe nobody else got this far with getting CKEditor 4.x running within a 1.10.x jQuery UI modal, but I find that a little hard to believe.
From what I can tell the following series of events occurs:
1. Click link activating the jQueryUI dialog
2. Click link for drop down within jQueryUI dialog
3. Upon clicking observe that the drop down did not appear, however appears the textarea is now selected
4. Click link for drop down within jQueryUI dialog
5. Upon clicking observe that the drop down now has appeared, however almost immediately it will disappear.
You can see from the above sequence that no event actually occurs which would cause a change in focus. It seems the drop down is disappearing after a timer goes off or something. I have no such timers in my code.
From here my next plan is to write up an isolated test on jsfiddle to attempt to get help finding a solution.
If anyone has ideas on what is causing this, would love to hear them. We are pretty close at having something viable.