Numerals in titles

[Imaginatorium]

Normal publishing practice requires that a title such as "Six pieces" is written like that, with the number in words. IMSLP seems to resolutely ignore this rule -- is there a principled reason for this? Personally I find things like "6 pieces in 2 volumes" make me shudder.

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[KGill]

Makes automatic alphabetization far easier, and ensures that the titles remain unambiguous to all no matter what language they were written in.