Colons in an anchor name

The spec currently defines an ns-anchor-name to be any ns-char except [ ] { } ,

To my eye, though, the following looks like it should be right:

states:
  - &wi Wisconsin
  - &il Illinois

population:
  *wi: 5 million
  *il: 10 million

But you'd need a space between the alias name and the colon to make it
match the spec. Why isn't a colon disallowed in anchor names (or at
least colon+space)?

Thanks,
Jesse Beder

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