See EscapeCharacterProposal for the discussion that led up to the current 1.0 specification.
Notes on the current specification:
The current example output for ~http://www.foo.com/~bar shows that ~bar is not part of the URL. This is unfortunate. How can we fix this on JSPwiki? -- AlexSchroeder
What happens in this situation: ~http://foo ~http://bar? My guess: Unintentionally the output will be: http:<em>foo http:</em>bar! This is unfortunate. How do you work around it? Oddmuse has a special workaround for this situation that is incompatible with the specification. -- AlexSchroeder