The thing about the reduplicative copula is is ...

The thing about the reduplicative copula is is that it’s redundant. And repetitive.

As early as the 1980s, a doubled “is” (called a reduplicative copula) became common in American speech {what I meant is is that …}. This is not the type of double that is sometimes grammatically required {what it is is a major ripoff}. Nor is it what comes out when one “is” refers to the word itself {That depends on what the definition of “is” is.}. Rather, it applies when the second “is” is grammatically superfluous {the thing that concerns me is is that I’m late}.

from http://taradiddle.tumblr.com/post/41498017/the-thing-about-the-reduplicative-copula-is-is-that