Multiple instances of the same ability clutter the display

Sometimes, the same ability is granted to a permanent by more than one source, but multiple instances of the ability are not meaningful. This is true for any activated ability and for many static abilities.

Take for example [LEA:46] Zombie Master: Other Zombie creatures have swampwalk. Other Zombies have "{B}: Regenerate this permanent."

With multiple masters in play, other zombies have these two abilities listed multiple times. It would be nice to show such abilities only once.

I don't know if MageSingleton is the right way to approach this. It seems fitting for a static ability like Swampwalk, since Flying, Intimidate, etc. are also singletons. I'm not so sure about the activated abilities because they are not enumerable (we can't make a singleton ability for each of "{B}: regenerate" and "{2}: regenerate" and all other possibilities, for example).