Problem: some unicode character combinations are invalid in paths when used together but not seperately
We tried to upload blobs with some character combination in the blob name. Some combinations got rejected both in the portal and using REST API
I tested with combinations of the following unicode characters
U+103A3 [OLD PERSIAN SIGN KA] 𐎣
U+FFFC [OBJECT REPLACEMENT CHARACTER] 
U+FE69 [SMALL DOLLAR SIGN] ﹩
Working blobnames:
unicode/_2weirdordering.txt
u/_2weirdordering.txt
u/_2weirdordering_2weirdordering.txt
u/_2weirdordering.txt
u𐎣_3/﹩_smalldollar.txt
Not working:
u𐎣_3/_2weirdordering.txt
u𐎣_345/_2weirdordering.txt
u𐎣_3_2weirdordering.txt
u𐎣_3/t_2weirdordering.txt
u𐎣_3/u𐎣_4/_2weirdordering.txt
When trying to upload these files through the portal you get "Failed to validate file names."
Upload through the REST API also fail for the same set of files.