Taradiddle

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

I’ve already complained loudly about this here, but lo and behold, Garner’s Usage Tip of the Day deals with this very matter:

is is.

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}.

Rarely is this form found in writing, even when speech containing it is transcribed. In any event, it isn’t an expression for careful speakers.