IDC's versus Egyptian format controls

[James Kass via Unicode]

Richard Wordingham wrote,

> And doing it reasonably well could be a lot of work.
> However, I don't see any good reason to discourage
> fonts from doing it by default, which is what is now
> being proposed.

Some people studying Han characters use the IDCs to illustrate the
ideographs and their components for various purposes.  For example:

U-0002A8B8 �� ⿰土土
U-0002A8B9 �� ⿰土凡
U-0002A8BA �� ⿱夂土
U-0002A8BB �� ⿰土亡
U-0002A8BC �� ⿰土无
U-0002A8BD �� ⿰土冇
U-0002A8BE �� ⿰土攴
U-0002A8BF �� ⿰土月
U-0002A8C0 �� ⿰土化
U-0002A8C1 �� ⿰土丰

It would be probably be disconcerting if the display of those
sequences changed into their respective characters overnight.  Such
usage might be limited to scholars and students, and a desire for
default composition might outweigh scholarly concerns, but IMHO to say
that 'doing it reasonably well at the font level would be a lot of
work' is a vast understatement.