Call for NNBSP replacement character in Mongolian Block

We have all be frustrated with the difficulty in working with the NNBSP in Mongolian. After our discussions last year and the kindness of the UTC to promote the changes to the NNBSP's feature set, I felt that we would be able to make the NNBSP fully usable. Over the last few months, however, given new problems encountered with NNBSP usage, I am ready to concede that it really needs to be placed within the Mongolian code-point space for reasons alluded to in the article below. I am seeking everyone's support for this move.
I want to express appreciation to the UTC for the considerable effort they went through to effect changes in the definition of the NNBSP over the past year. These changes will no doubt help in the interim as we look to the possibility of a replacement to the NNBSP's function in Mongolian usage.
We plan to make the following proposal at the WG2 meetings next week in San Jose.
Comments are very welcome,
Greg


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Call for New NNBSP character in Mongolian Block
Even with the changes that were effected in the NNBSP re-specification (Unicode version 9.0), there are still deficiencies in proper functionality. These deficiencies include the following:

*        Display problem if Fallback Font includes its own version of the NNBSP (U+202F). This problem occurs at the Application level.

*        Certain applications such as PDF viewers will drop the NNBSP upon cut & paste as well as other operations
As much as we fix the NNBSP in Mongolian to display correctly in different situations, we continue to find more areas where it will fail. The most recent finding over the summer was that given an application that is displaying Mongolian text AND given a font selection that is not a proper vertical Mongolian font AND given NNBSP+Suffix forms in the text AND given a fall-back font that uses its own NNBSP, the display of the suffixal forms will fail. The reason is that the fall-back font definition of the NNBSP does not include the OT rulings to do proper and necessary substitutions based on the NNBSP context.
There is considerable frustration in the Mongolian user community with the ongoing problems we are having with this one control character. At the same time, we see much momentum in the Mongolian community to adopt the Unicode encoding if it will work correctly. This is significant as there are huge swaths of Mongolian text using ASCII legacy era vertical Mongolian fonts. We cannot miss this moment of opportunity to provide a simple solution to this one biggest trouble of our Mongolian encoding - the NNBSP. It is felt that once an NNBSP-replacement is encoded within the Mongolian block, both rendering engines as well as fonts will be able to exercise adequate control as to display suffixal forms correctly.
I am calling for a new control character "Mongolian Suffix Connector" placed at U+181A to replace the current functionality of the NNBSP (U+202F) in Mongolian contexts. Transitional fonts, of course, would have to implement both the NNBSP as well as the replacement control character for backwards compatibility. Keyboards could be changed to use the new control character instead of the old NNBSP mechanism. Even if it took a considerable period of time to cast the encoding, I think all parties dealing with Mongolian vertical fonts will embrace this move.
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