no dedicated section in JLreq, used in several text on spacing or line breaking. These texts are fine to be removed along with deletion of cl-24 (better to be mentioned in change log).
Character classes 20, 21, 22, 23, 25, 28, 29, 30 can be removed by defining their behavior in the descriptions of related features. (also see items below for 21, 25, 30)
All these features require specific tagging and therefore the behavior would belong to these tags rather than to the characters.
Should probably be covered by text layout rules for other languages or specific domains (e.g. math)
There might be other similar cases in JLreq, and need further investigation.
Related to cl-30 Characters in tate-chu-yoko, tate-chu-yoko block can be treated just as a single Kanji in terms of layout, and some text should be added (to item 3.2.3.c or somewhere). (There seems some special cases for consecutive blocks, like Appendix C.2.13.)
The description of the behaviour of Kanji numeric is scattered in JLReq. It would make sense to add a subsection to describe it in one place.
(From JL-TF meeting 2020-10-20)