That's the grammar of the joke form I was using. And what?

And what’s wrong with that exactly?

Sometimes it's OK, but in the context of the post, it is inappropriate.

But you happen to be wrong.

Except, not.

But it is, for the simple reason that there is no grammatical rule about starting a sentence with and, but or even because. You can use them as a deliberate device to add further information as an afterthought. It's one of those things we were told at school (I was too) that was actually false.