@tkoeppe , please have a look. This is for consistent application of \iref even with multiple cross-references.

The patch is a visual no-op except for a few situations where a linebreak now happens elsewhere (because breaking before "(" is now discouraged) or where whitespace is different because ~ got turned into a normal space. The former doesn't apply extra spacing after (end-of-sentence) periods.

The effect looks good, but I worry a little bit about creating some excessively complex implementation. Do you think this feature is worth the price?

Which price? This seems pretty straightforward in LaTeX3 terms.

Plus we get the benefit that we have a consistent handling linebreaks / spacing with xrefs for both "(1.2.3)" and "(1.2.3, 4.5.6)" cases.

@tkoeppe, rebased

OK. I've caught up on the history of LaTeX3 (it's come quite some way since I last followed it), and it seems that what you're doing here is at least somewhat normal and stable, and there's no reason to not use those new features.

Feel free to rebase and merge!