> Any application which bans or prevents the interchange or storage > of PUA code points should be considered non conformant. > > Any application which substitutes missing glyphs for PUA characters, > when a valid font which covers those code points is active, > should be considered non conformant.
I see no reason why a protocol cannot introduce a higher-level rule which prohibits the use of PUA characters. Not only do I see this as being implied by the fact that a protocol can apply whatever meaning is appropriate to PUA characters (therefore why not "non-character"), but I can see a point in doing so in a protocol which by its nature is not suitable for customisation. This isn't to say that I think its necessarily a good idea to do this when designing a protocol - I would want to see a clear problem clearly solved by doing so. I'll also add that if a protocol was intended to allow free exchange of textual content then it should not prohibit use of the PUA. However if it is intended that any user of the protocol would be able to infer the same meaning from a message as any other user then it might be worth considering. > Since the PUA is for consenting adults, any application which restricts > PUA use is effectively precluding consenting adults from reaching > and implementing their private agreements. Consenting adults can say no.
