In the absence of instantiation limits, whether a C++ compiler
will halt when compiling a given program is undecidable.
(Todd L. Veldhuizen)

Once I heard that codepoints in Unicode are given away carefully.
On the other hand, there are codes for ʇxǝʇ-uʍop-ǝpısdn, 𝔉ℜ𝔄𝔎𝔗𝔘ℜ, 𝐛𝐨𝐥𝐝 𝐥𝐞𝐭𝐭𝐞𝐫𝐬, 𝒮𝒸𝓇𝒾𝓅𝓉, and a lot of other weird stuff. There are characters reversing the text direction.

No doubt this could be useful. But on the other hand, I dont know if its really a good thing to have symbols that are basically letters in another font as standard unicode characters.