Mastodon: IDN domains don't render correctly in usernames

[wxcafe]

IDN domains in usernames are displayed as punycode in usernames in the web interface, which isn't the intended result.

here, for example, "@[email protected]" should be displayed as "@TransPosees@pénibles.transposées.eu"

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• [x] I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• [x] This bug happens on a tagged release and not on master (If you're a user, don't worry about this).

[barzamin]

If there are objections about confusables, it is possible to fall back to punycode when potential confusion is detected, but, otherwise, render the URL as full unicode.

Refs:

Since version 22 (2013), Firefox displays IDNs if either the TLD prevents homograph attacks by restricting which characters can be used in domain names or labels do not mix scripts for different languages. Otherwise IDNs are displayed in Punycode. [10]

[wxcafe]

it would also be possible to follow the rules that are basically only accept utf8 chars that are used in the writing systems accepted by the TLD, which remove basically all possibility of confusion without alienating everyone who doesn't want to use english domain names.

[sneak]

I think it needs to be more permissive than that. I use the domain hæresiar.ch (a domain hack), and the æ ligature is not endemic in Swiss orthography.