Hmm, this is a case where HN’s title mangling changed the meaning of the title. Lower case delta (δ) is used intentionally. I don’t think HN should automatically modify the casing of non-ascii chars.
The submitter has a grace period of a few minutes to edit the title after submitting, so there's no need to change what HN does
Email [email protected] and they'll fix it.
Even for ASCII chars, nomenclature in math and physics is usually case-sensitive.