Names of all things shall conform to [a-zA-Z][0-9a-zA-Z]* lest one anger the old gods.
But you might smile and feel a little nostalgic seeing an old timer plowing data in the modern era, just be careful not to spook him with any of your new runes.
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yes, non-punycode domains may not start or end with dashes and must not have consecutive dashes
the consecutive dashes in punycode were done on purpose so that the new internationalizing punycode domains couldn't conflict with any existing domain.