Only top level domains (ccTLD) that are white listed appear as readable names. Otherwise you see punycode.
The рф TLD is one of the domains that have been white listed (network.IDN.whitelist.xn--p1ai) and thus doesn't appear as punycode.
The .com TLD isn't white listed (and probably never will).
See http://www.mozilla.org/projects/security/tld-idn-policy-list.html

You can check the IDN prefs on the about:config page.

See also:

• http://kb.mozillazine.org/network.IDN.whitelist.*

(fixed KB link - c)

what is the criteria of white-listing tld's that Firefox is following?

Two of those links don't lead anywhere.

That last link should be:

• http://kb.mozillazine.org/network.IDN.whitelist.*

If you want to whitelist the .com TLD then you can create a new Boolean pref network.IDN.whitelist.com and set the value to true

• http://kb.mozillazine.org/about%3Aconfig

This blacklisting .com IDNs is not logical at all.

We run popular site with few milion PV each month, that use word with special character in our local language (polish). Our service use .com extension to reach all users in the country and accross the globe, but since Firefox is not allowing to use .com IDNs, we are forced by FF (for now) to use incorrect spelling.

I'm not sure why FF thinks that this right solution? Why FF is hiding behind story about spoofing? We are not spoofing but we are punished for some reason. It is easy to use for ex. citbank .com for spoofing and FF is not blocking those, are they?

Why legitimate business such ours, need to suffer because FF stupid policy? I spoke with many enterpreneurs in my country and they share the same view. Lack of compatibility makes you less competitive and less usable in our eyes.

For now till .com IDNs are included in whitelist, we'll deploy banners to all our high traffic services (which generates over 7 mln PV / month) to inform our visitors to NOT USE Firefox browser, and download any other browser instead.

If FF is not helping to grow our business, we are not going to help expand FF.

That is not about logic, but about security.

The company that manages a top level domain must meet strict conditions about not allowing specific characters in domain names to prevent spoofing by using similar looking characters or other ways to mislead visitors. I'm sure that you do not want that someone else registers a domain that looks almost the same as yours, but leads to some spam or malware hosting site. The .com domain doesn't meet those conditions and is therefor not white listed.

This link doesn't lead anywhere either

network.IDN.whitelist.com

That is not a link, but caused by how this forum works. It almost makes every phase with a dot a clickable hyperlink.

@ cor-el <"That is not about logic, but about security."

This is lame excuse and you know it :)

Firefox already allows IDNs from their whitelist to use characters that are simmilar.

Let's get for example two words, same meaning (loans) correct spelling in polish is: pożyczki.pl and incorrect spelling is pozyczki.pl With .com you can't use correct speling pożyczki.com because FF is blocking CORRECT spelling.

Another example...two words with different meaning sad.pl (orchard) and sąd.pl (court). You can't use sąd.com in firefox even that this is CORRECT spelling.

I don't want browser developers to limit use of domains in the name of fight with spoofing, bause they don't know local markets and language enough to pass correct judgement. There is ADR, WIPO, OHIM, USPTO and local police to deal with this matter, and its working. Those institutions are locking domains that are used in bad faith. It's not FF job to do it.

FF is the last browser to lock IDN .com, and taking in consideration growing IDN internet markets...FF will lose even more international users if they'll keep blocking LEGITIMATE & CORRECTLY spelled words with diacritics in .com extension.

Works for me in Firefox with network.IDN.whitelist.pl enabled.

• http://www.sąd.pl/260,-------------.html

Seriusly? Did you read what I wrote?

Try to go to sąd.com or pożyczki.com

Both legitimate and CORRECTLY spelled words. How come FF block users from using global .com extension in their native language?

He posted a .com and you are saying the country code works. WE KNOW THAT.

 What we don't know is why Firefox can't get the #%$#%$#%  dot .com's and .net's to work.  Don't bother answering with your schtick about the whitelist. Nobody cares,  I just want IDN's to work.