[lpcvoid]

The library bought those books and as such possess the physical copy. If somebody vandalizes it, that's destruction of property and bad.

Reddit never paid anybody. Reddit is made up of comments made by people, and those people can decide to delete these comments. Reddit is a for profit company looking to squeeze maximum shareholder value from the value provided by others people comments, and doesn't enjoy the same leniency that a public library would, IMHO.