Not very accurate
Perhaps the author should read and understand RFC2396 and then rewrite the last section of his article. In that reading and understanding he might want to notice that the RFC is about URIs not about URLs, that section 6 says nothing at all about case sensitivity being required in any component of a URI (it does point out that it can't be required in certain components, but that doesn't mean it is required in the components not mentioned), and that section 2.4.2 leads straight to URIs in the http scheme that differ in case in teh file component of the URL and are required (by the escape rules) to identify the same resource (for example http://abd.com/a%2bc locates the same resource as http://abd.com/a%2Bc despite the case difference between b and B). His claim that the RFC unambiguously defines URLs to be case sensitive in the file part is pure balderdash. Maybe he could read appendix G, which says quite clearly that this RFC doesn't define any URL schems?