[a_e_k]

> The only problem is that, in the name of not breaking backwards-compatibility (or something like that), the archaic defaults have remained.

As a user since '97, I've often felt that this philosophy is entirely, well, backwards. I know how to read the release notes to learn of such changes and how to edit my personal init.el file to revert a setting if I don't like the new default. As long as no one takes away the option, the default doesn't really matter too much to me. But newcomers who might not yet be comfortable with editing their init.el files could really benefit from a more optimal out-of-box experience.

(And besides that, often the newer option is something that I've already moved on to, so making it the new default means I can now remove it from my init.el. I always enjoy when I discover that I can cut something from my init.el because it's now in base Emacs.)

[drdexebtjl]

One solution that I really like for that is having the user configuration carry some kind of version number.

Then, to change a default from `old` to `new`, you instead change it to `configVersion >= x ? new : old`, and add some kind of non-fatal warning in the else case instructing users to set their config to `old` explicitly.

You don't break people's setups, they become aware of new defaults without reading release notes, and new users get the new defaults.

[a_e_k]

I do like that general idea. I bet it would be possible wrap in a handy elisp macro.