Per the Gnu Coreutils NEWS file: All commands now markup option names in --help and man pages, with bold attributes, and hyperlinks into the online manual on gnu.org. The links can be configured with the --enable-manual-url configure option, and the bold highlighting with --disable-bold-man-page-references. At runtime all markup can be disabled with the TERM=dumb env var value. This has nothing to do with less (or bash or fish). It is a new behavior as of Coreutils 9.10. It is to preserve the hyperlinks in the help output of ls, cp, rm, mv, etc. In default mode, less catches these control codes and escapes them so you see the visual escape codes. If you use less --raw-control-chars then less is NOT escaping the control characters (just passing them through) and they get interpreted by the terminal as screen formatting codes. Debian 13, which ships Coreutils 9.7 does not have the change and cannot reproduce the behavior.