We should begin by discussing whether we really want this feature, by
default or otherwise. One of the aspects we need to consider, IMO, is
what do spell-checkers do with these characters: if they don't treat
them as word-constituents, that would be one argument against the
change; if they do, it's an argument for the change.

At least aspell now seems to accept curly quotes by default in some locales.

However, I think the rationale for the feature is independent of spell-checkers. Emacs has had support for displaying curly quotes for some time. There are various ways to enter them conveniently (the Emacs Wiki lists smart-quotes.el, which I use, and typopunct.el. The sole author of smart-quotes.el would be quite happy to assign copyright to GNU and have it added to Emacs; I suggested he contact the maintainers about this in August 2011. (Incidentally, I'd be happy to facilitate the process if Emacs maintainers were interested.)

Since curly quotes make perfect sense as part of words, in exactly the same way as straight quotes, it seems reasonable to treat them the same for movement, even if spelling support is not yet perfect; indeed, any additional incentive to spelling program authors to improve Unicode punctuation support is welcome.

For writing text, the introduction of Unicode has been a boon, and it would be great if Emacs's "semantic" support would catch up with its excellent display support. This is one aspect of that.

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