(Doug wrote on bug 27860 comment #9)
There was never any reason to make this change. The correct change as noted by
Nemo_bis, was to uncheck the box by default and possibly remove the option to
change this to checked by default, not remove the box from new pages
altogether. Nobody ever really asked for that change; two alternatives were
presented and one was simply implemented without comment as to why that was
perceived as the better alternative.
Additionally, the original problem was characterized as being for making a "New
Section" not creating a page, a new section to an already existing page is
actually less likely to be minor than a new page is. This should be reverted
unless there is a wiki that thinks it actually needs it to be turned on - that
is that they never have minor page creations even for redirects - unless you're
a bot, bots can still create new pages as minor.
The new behaviour of the preference must be triggered by a new configuration variable, false by default.
Target milestone 1.20.x as this catastrophic behaviour change for such an important preference should not affect more releases.