> > > That sounds like a non-conformant use of characters in the U+24xx block. > > Well, you are an expert on these things and I do not understand as to with > what it would be non-conformant. > > A conformant process must interpret ⓅⓊⒶⒹⒶⓉⒶ as the characters ⓅⓊⒶⒹⒶⓉⒶ and not as a signal to process what follows as anything other than plain text.
What you are proposing is a higher-level protocol, whether you realize it or not. Unfortunately your higher-level protocol has a serious flaw in that it cannot represent the string "ⓅⓊⒶⒹⒶⓉⒶ". Also, seeing a bunch of circled alphanumeric characters in a document ⓘⓢ◯ⓕⓐⓡ◯ⓕⓡⓞⓜ◯ⓤⓝⓞⓑⓣⓡⓤⓢⓘⓥⓔ. There are plenty of already-existing higher-level protocols (you mentioned one: XML) that could be used to provide information about PUA characters, and they are all much better suited to that purpose than what you are proposing.
