Giving books as presents
Inscribing books that are presents
Crossing out the price on books that are presents
Inscribing a book, if you're not the author, is a crime against humanity. As is defacing a book by scribbling or cutting it in any way.Disgusting.
I'm okay with flyleaf inscriptions by gift-givers, but only the author(s)/editor(s) should sign the title page.
More or less my view. The author gets the title page, gift-giver gets jacket or (my preference) the half-title.