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Dave and I share the goal that interop never be reduced to simply a statement to the effect of "works with the dominant vendor". That's why I have been delighted to find Keith, JHawk, and Mike to be joys to work with. The few times I have identified discrepancies between their early implementations and the specifications, my reports have been eagerly and cheerfully accepted and quickly addressed.
I can't help but contrast this with the reaction to Mark Pilgrim's report of discrepancies between the OPML specification and the actual documents that are being produced today.