Hugo 0.60 has switched to using the Goldmark markdown generator. It broke curly quotes and punctuation. It’s a known issue, and persists as of 0.60.1.

The official docs list these as options for your config file to enable support, or you can enable the old default markdown handler. But no combination of the below works:

defaultMarkdownHandler: blackFriday
markup:
  goldmark:
    extensions:
      typeographer: true
  blackFriday:
    angledQuotes: true

So stick with 0.59.1 if punctuation is important to you.