How to work with characters from CJK Unified Ideographs Extension B correctly?

Question

Background:

Recently I'm trying to deal with some Chinese characters which belongs to the CJK Unified Ideographs Extension B block. The motive comes from some further interest following a former question, and some ideas of using Mathematica for typesetting ancient Chinese scriptures.

Edit:

Here is some sample code which looks fine at first sight ( The Unicodes of the three characters involved here are x20027, x200D5 and x20137. The setting of the $SystemCharacterEncoding of my Mathematica is "CP936". ):

But after saving then closing the notebook, I re-opened it, without touching anything, the Front End displays weird now (and note the attendance of the syntax errors):

It seems the Front End is not able to correctly render them.

Furthermore, although I can create a textcell looking fine:

whose CellExpression is:

Cell["\:d840\:dc27\:d840\:dcd5\:d840\:dd37", "Text", CellChangeTimes->{3.5359048507534103`*^9}]

but if I trig Ctrl+Shift+E and edit the CellExpression directly (eg. deleting the CellChangeTimes item, which should not affect the "appearance" of the cell), then convert the cell back to normal status, things get wrong again:

This kind of problem never happened when dealing with characters from CJK Unified Ideographs and CJK Unified Ideographs Extension A blocks, so I guess there may be a bug here.

So my questions is: While I do realize the "Unicode" encoding in Mathematica referring to only 16-bit Unicode while the CJK-B begin with x20000, is there any method to render and work with characters from CJK Unified Ideographs Extension B correctly?

Answer 1

Reposting John Fultz’s comment above as a “community wiki” answer for everyone to improve:

Mathematica simply has no support for non-plane-0 characters. That it appears to temporarily work should not fool you into thinking that M-- knows anything about such values. Those who saw the R&D keynote at the 2011 Tech Conference may remember my relating the story of the pain we have experienced from the fact that we were extremely early adopters of Unicode, well before it was baked into OSes and the concept of Unicode planes had been fully developed. It affects every part of the system, and will be difficult and expensive to fix when we finally do fix it.