Only arguing on the classification of this bug here. Let's call a cat a cat. When something doesn't work as documented, it's a bug, not a wishlist entry.
AFAICT, there's nothing in the GNU coreutils documentation that states that pr only works on input that consists exclusively of single-byte characters that are neither zero-width (though it copes OK with ASCII BS and TAB) nor double-width (or on ASCII-only input). Today, UTF-8 is the most commonly used character set, so it even affects English text (where £ (the British currency symbol) is encoded on two bytes in UTF-8 for instance), and even US-English text like for the ‘quoting characters’ (3 bytes each in UTF-8) now that ASCII ' has been demoted to just an apostrophe. That can also be seen as a POSIX conformance bug (though GNU coreutils doesn't claim POSIX conformance, only "The GNU utilities documented here are /mostly/ compatible with the POSIX standard"). $ pr -tm --sep-string='|' <(du --version) <(truncate --version) du (GNU coreutils) 8.25 |truncate (GNU coreutils) 8.25 Copyright (C) 2016 Free Software Fo|Copyright (C) 2016 Free Software Fo License GPLv3+: GNU GPL version 3 o|License GPLv3+: GNU GPL version 3 o This is free software: you are free|This is free software: you are free There is NO WARRANTY, to the extent|There is NO WARRANTY, to the extent | Written by Torbjörn Granlund, David |Written by Pádraig Brady. and Jim Meyering. | -- Stephane