The Unicode Consortium Discussion Forum

Here's the fact I know:

1. UTR#50 draft #5 sets Tr, and the proposal from MS was Tr too.
2. All the today's font don't have vert for this code point, so it means it will result to U at least for a while.
3. Having Tr can recommend future font developers to put sideways vert table. This can lead to inconsistencies by when the font was designed.
4. MS Word sets it U.
5. fantasai believes it's U.
6. One vendor I know believes it's R.

Given #2 and #3, I don't think having Tr is a good idea. If I understand correctly, the spec says Tr is supposed to be where the most current font have vert, and it contradicts with it.
I have mild preference to U given #4 and #5, but R also makes sense if we consider consistency with U+FF1D FULLWIDTH EQUALS SIGN.