\[~tamas.vajk], I flipped this around from the original proposition; the real problem is that you subscribed with an anonymous delegate. Hopefully that's not too much harder in the implementation...
\[~ann.campbell.2] We won't be able to implement the rule this way. Finding subscription and unsubscription pairs won't be easy.
On the other hand, whenever you try to unsubscribe with an anonymous delegate that is an issue. So recognizing this is easy. I would go this way. (I've changed the location of the issue, but both the message and the title would need modification)
