Well, it isn't prohibited, so I guess you will need to be forever vigilant in view of the possibility that somebody might get it in their head to encode some combining mark that isn't already accounted for in Tibetan *and* that they would simultaneously insist that a precomposed form of that mark applied to a two-part Tibetan vowel need also be encoded (despite the fact that the precomposed two-part vowel is itself discouraged from use and the sequence could be represented by the individual pieces, which is what all the Tibetanists want to do anyway), *and* that nobody on either encoding committee would be paying any attention and view this as a fishy thing to do, *and* that nobody would notice there was a problem during the international balloting, *and* that nobody would raise a stink during beta review when their Tibetan normalization implementation raised exceptions.
Dumb things can and occasionally do happen to the standard, but I'm not losing much sleep worrying about this particular dumb thing happening. Trying to legislate against anything dumb happening by adding more and more stability guarantees has its own set of risks and downsides, in part because the Unicode stability guarantees are only seen as binding by the Unicode Consortium, and are not recognized in the ISO process. --Ken > No. I am trying to confirm that there will never be any character but > U+0344, U+0F73, U+0F75 and U+0F81 that has a non-singleton canonical > decomposition to non-starters. The only way I see can for that to > happen is a decomposition via one of U+0F73, U+0F75 and U+0F81 such as > from U+E4567 to <U+0F73, U+E4568>, and I cannot see where this is > prohibited.
