What has changed in MacOS 10.12 in handling code pages?

[Kay C Lan]

I was thinking that this might have something to do with the installed
fonts you have and maybe some sort of substitution if the font you
used with your pre-10.12 install is not available with your new
install.

Interestingly I've just done a test and got a rather unusual result
when trying to test this theory.

In LC 6.6.5 on OS X 10.11.6 I created a new stack, dragged a field
onto it (i.e. no font specified for the field) and then in the msg
box:

put the effective textFont of field 1
--the result is 'Lucidia Grande'

In LC 9.0.0 dp4 on the same machine if I do the same thing the result
is '(Text)'

If I go into the LC 9 Object Inspector to set the Font of the newly
created field there are a bunch of entries at the top, which you don't
get in 6.6.5, like:
(Default)
(System)
(Text)
(Styled Text)

If I choose a specific font then understandably doing:
put the effective textFont of field 1
-- result is whatever specific font I've chosen.

In the Dictionary the LC6 entry differs from the LC9 entry but both
contain this statement:

On Mac OS systems, if the specified font isn't available, the system
font (which is set in the Appearance control panel and specifies the
font used for menus) is used.

I think that is an old reference to the Classic OS as there is no such
thing as an Appearance Control Panel anymore and you can't set the
font of menus.

I'm still leaning towards what fonts you have installed, maybe 10.12
handles substitution differently than 10.11 and earlier. And somewhere
along the way LC has changed the way it handles and reports situations
where no font is specified - as there are obviously now more default
possibilities and the Dictionary doesn't explain how you might end up
with (Default) as opposed to (Text)