I noticed odd arrangements of my control chars, and checking their info I found that lefttorightmark, righttoleftmark, zerowidthjoiner, and zerowidthnonjoiner are catogoriezed as Separator, Nospacing, while the rest of neighboring control characters are Separator, Format.
Also graphemejoinercomb and VS1 to VS16 are categorized as Mark, Nospacing, while Separator, Format like the others seems appropriate.
It probably does not matter in practice, but it feels odd not to have all these control charterers in the same place.