A feature is what ever you make it out to be by definition. You could call a text field or a button a feature if you wanted to.

I just think that closing your account is something more fundamental that being what we traditional think of as a 'feature'.

Ah, but you can delete your Yammer data. You just can't do it in batch.

It's not a priority anywhere to implement batch features, even if it were the opposite---batch additions.