Unicode disagrees about IJ and ij… although there are glyphs for them, they are "compatibility decomposable characters" which basically means they are deprecated. The rendering software should handle proper collation, capitalization, etc. without using the digraph glyphs (e.g. Firefox gets this right).
(A similar situation applies for English di- and trigraphs such as "ffi" and friends.)
(A similar situation applies for English di- and trigraphs such as "ffi" and friends.)