Steve Bennett wrote:
ISBN is different: the parser deliberately tries to detect text that the user typed naturally ("ISBN 123456789" being the normal, unmarked formatting used in the real world) and treat it specially. It's not a real grammatical feature, it's a deliberate effort to achieve markup with no effort.
The only other feature I can think of that works that way is bare urls: http://foo.com
Anyway, it's not a major issue. There are bigger fish to fry.
Steve
It also works for RFCs.