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cupsctl removes comments and empty lines from cupsd.conf
When user calls cupsctl, f.e. cupsctl --remote-any or cupsctl --debug-logging, almost all comments and empty lines removed. Probably ignoring empty lines could be fine, but removing comments IMHO reduces readability.
By the way:
This is the reason why I personally never use cupsctl.
Strictly speaking this is even a critical bug because
user data (user comments in config files are user data)
has to be sacrosanct - always.
As far as I know cupsd.conf is still also meant for users
to manually specify their settings (when cupsd is not running).
FWIW, the reason its been implemented this way for so many years is to avoid having the comments get out of sync - for example (from the stock cupsd.conf file):
# Log general information in error_log - change "warn" to "debug"
# for troubleshooting...
LogLevel warn
Also, If you do decide to preserve comments, don't add new ones... :)
I'm pushing this to CUPS 2.5 because this isn't something we should try fixing in a patch update.