That’s the end of a sentence allegedly uttered by Winston Churchill to demonstrate the absurdity of a grammar “rule” we’ve all heard. There are several variations attributed to Churchill, but the one I like best is at Thinkexist.com: “The rule which forbids ending a sentence with a preposition is the kind of nonsense up with which I will not put.”
I confess I did not know this rule was mythical (I had it drilled into me by my high school English teacher), and most of the time I think the “with which” construction can sound OK. But knowing that others find it annoying, I will probably avoid it in the future. Plus, as some of the commenters at the post point out, one can follow the rule and still avoid stilted sentences by exercising a little creativity.
It’s worth looking into. (See, that sounds a lot better than “It’s a post into which it is worthy to look,” doesn’t it?)