I've removed the automatic substitution of – and — for hyphen sequences from 1.5, as it seems to simply cause a neverending sequence of breakage of links and markup. The special cases that were added to try to keep it from breaking (some) links and (some) markup of course made it behave fairly inconsistently, and on the whole it seems to have been causing trouble far outweighing the utility of making some dashes slightly more attractive.
Perhaps some future parser that operates in a clean fashion instead of layering regexes on top of each other will be able to do this in a consistent, non-breaking manner. For now it doesn't seem worth it.
-- brion vibber (brion @ pobox.com)