Got any examples of internationalized domain names that would be affected?
I don’t speak any languages that don’t use the Latin alphabet. This is true of millions of other people. So for those kind of users, I guess network.IDN_show_punycode set to true won’t cause any inconvenience? I guess it wouldn’t be hard for Firefox to ask the user at first start of to guess that information somehow?
As for internationalized domain names… User who speak languages that don’t use Latin alphabet, couldn’t there be a different solution? How many domain names exist that mix Latin letters with non Latin letters? I guess for other domain names that use alphabet XYZ, just allow alphabet XYZ. I didn’t look into it but perhaps there aren’t many cases of mixing Latin letters with non-Latin letters?
In short: we are users of popular webapps. We don’t have resources to fix issues in these.
Longer answer: see this this: Privacy Policy Technical Details - Kicksecure
and related discussion: Wiki search fallback suggestion - #6 by Patrick