cda,
I've read the commentary and I'm not trying to be difficult with you but what do you think they mean by "The extent of the protection provided would not be regulated." The example earlier in that paragraph mentions "certain areas". It sounds like they are acknowledging that a building owner could provide a non-required system in any space of a structure and it's acceptable as long as the installation of that system, ie. spacing, piping, inspection, monitoring, materials, testing, maint, water supply . etc would need to meet the requirements of NFPA 13 or 13R. Is it just bad language in the commentary?
Have no clue
But in the beginning to me it says if installed shall meet 13
plus the base language supports it.
And that section is not exclusive to fire sprinkler systems