It isn't that I don't want sad things to happen to the characters in my book. It's just that I turned the page in the middle of one character talking and there are no more pages. The sentence caught mid-page-turn didn't even punctuate to conclusion. The absence of pages doesn't tell a story, it leaves the reader wondering where the rest of the story is.
And the reason it's so jarring is that the writer didn't finish erasing the end of the story. You can see stuff clearly connected to what would have been the rest of Karlach's story through Act 3, that you just don't get to do anything with. Maybe those things DO lead to a realization of an inevitable tragedy, but until the story is finished that tragedy hasn't been earned.