In xml mode, mark the following: and execute comment-region: This is invalid XML because '--' is not allowed inside comments. See http://www.w3.org/TR/REC-xml/#sec-comments. (This is enforced by for example XML::Simple in perl 5.10.) For example, as an alternative, the following is valid: The offending code seems to be comment-quote-nested in newcomment.el. Should this code be changed, or the code for the xml mode, or both? In GNU Emacs 23.1.1 (i686-pc-linux-gnu, GTK+ Version 2.8.11) of 2009-09-08 on deacxl001 Windowing system distributor `The Cygwin/X Project', version 11.0.10800000 configured using `configure '--prefix=/app/emacs/23.1/LMWP2'' Important settings: value of $LC_ALL: nil value of $LC_COLLATE: nil value of $LC_CTYPE: nil value of $LC_MESSAGES: nil value of $LC_MONETARY: nil value of $LC_NUMERIC: nil value of $LC_TIME: nil value of $LANG: en_US value of $XMODIFIERS: nil locale-coding-system: iso-latin-1-unix default-enable-multibyte-characters: t Major mode: XML Minor modes in effect: tooltip-mode: t tool-bar-mode: t mouse-wheel-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t global-auto-composition-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t line-number-mode: t transient-mark-mode: t Recent input: M-g g 3 0 6 C-SPC M-; C-a C-SPC M-; C-x C-s M-x r e p o r t - b u g Recent messages: For information about GNU Emacs and the GNU system, type C-h C-a. Mark set [2 times] Mark activated Saving file /vobs/radio_testbeds_adv/platform/testapps/build/template/dul_a/ulma_1/make/template.xml... Wrote /vobs/radio_testbeds_adv/platform/testapps/build/template/dul_a/ulma_1/make/template.xml