> but if I had a choice I'd do the original design so that it avoids MI.

Do you always have the choice (even with hindsight)?
Assume these four entities (with the methods they need to implement):

Person
:FeedMe
:WaterMe

Cow
:FeedMe
:WaterMe
:EatMe

Cake
:EatMe

Deadly Nightshade
:WaterMe

What will be your class structure?
Given a collection of such objects how do you know which are edible?
What if the calling entity is sometimes a vegetarian?