We picked up this heart-string tugger at our public library recently. The cover was innocuous enough, so I let the kiddos read it first, not thinking anything of it.
After my freshwoman finished (she was the first to get her hands on it), she came to me, all serious, and said, "Mom, you have to see this."
I have honestly never seen this done to a book before, and we do a lot of public library reading. Obviously, someone took great pains for it to match the font and to make it look like typeface. It appeared in at least eight or nine places, where a profane or foul word or phrase was used by adult characters. Thought went into the replacement words. I haven't seen the word "tar," as in "tarnation," used in children's literature in a very long time. Immediately, I wondered, why take such care in defacing a book?
I will say, the original language is such that, if I were reading it outloud, say at bedtime storytime to my kiddos when they were younger, I would have left the words or phrases out as I read. I was never one to substitute on the fly. I might leave them out even now, with one of my two children in high school (and yes, we still do bedtime storytime!). We don't use that kind of language in our home, period, but my oldest reads it in school all the time.
However, would I have defaced a book (because make no bones about it - that's what this is, defacement) like this, ruining the reading / story experience for other, unknown library patrons? No way.
The rules of where to draw the line at profanity in text (not allowed in picture books, expected in YA, leaving MG in the middle, somewhere), are changing and have been changing since the 60s. There's an excellent discussion of writers using swear words in MG fiction here. As you might expect, I'm solidly in the "create a character- or setting- specific creative swear" camp.
But we know know children frequently read-up, and I remember well combing the library shelves for material that was both emotionally and contextually appropriate for my advanced-reading level kiddos.
I can only speculate on what would motivate someone to do this, but perhaps it was a reaction to the incongruity of the adults' language with a cover that's so artfully kind? The MC is 11 and the cover is gentle and soft, creating a parental or reader expectation that perhaps did not mesh with the text. That's the point of the story, however - juxtaposing the cruelty of adults with the kindness of children.