> Instead of checking for "understands" we should use valueOfFlag: (which
> defaults to false) to get back the old behavior.

Hmm, I'm not sure "false" makes sense as a universal default value.
Apps typically choose their own lazy-initialized values
attribute-by-attribute, and usually based on it having been nil.  This
is a very common pattern for apps to hardcode their own defaults with
an ifNil: ["whatever"].

> Or we recreate the
> preference.

Sure.

> Or we make it into a "pragma" preference on some class (which
> seems to be the preferred way nowadays, even though it leads to an explosion
> of pref accessor methods?)

*Thank you* for leveling a fair critique at pragma preferences.  IMO,
they are preventing the emergence of simple and powerful abstractions
in our Preferences framework while, as you alluded, making lots of
code.  :(  Their real benefits deserve some scrutiny.

> What would be best?

This.

   http://lists.squeakfoundation.org/pipermail/squeak-dev/2016-March/188486.html

Best,
  Chris