Dedicated power lines-getting started

Oy. I don't know how you can infer that from reading this paragraph of the code. The Belden FEP dielectric is rated to 600F, and thus extremely safe for plenum use without a conduit. Its voltage rating, even at 300v (I thought it was higher), is still comfortably above the 120 it's used for.
You can even run it at 240.
The 600v issue is moot. I have seen several professional installations of 8380x that were not at all questioned re legality or hazard. 12AWG, all Teflon and copper. What's to worry? The stuff sounds GREAT, and is a couple bucks/foot.
If you're worried about an inspector not liking the 83802's twisted shield used as a bus ground, then spend the extra 50% on the 83803. End of story. $18/ft? The only stuff that I've seen that I'd like to see that perhaps REASONABLY approaches value at this cost is doubling or tripling up on the silver-coated Teflon 16AWG stuff Belden makes for a bit over $4/ft. That'd be $9/ft wholesale for 13AWG, or $13/ft for a bit bigger than 12AWG. 83802 is 1/8th the latter, and thus most reasonable for dedicated lines. Using the silver stuff might be interesting for PCs, though, eh?

From NEC Article 760:
"... The voltage rating shall not be marked on the cable. Voltage ratings marked on the cables may be misinterpreted to suggest that they can be used for Class 1, electric light and power applications. ..."

Did you really read it?
Look at a length of NM wire, it has 600v printed on the jacket. Art. 760 says printing 300v on the jacket is prohibited because it could lead to a misinterpretation of the intended use which does not include what you are proposing to use it for, power applications.

I have a definitive answer from someone who actually knows the National Electric Code and where to look in the NEC, chapter and verse. I would be glad to forward the information to anyone interested.

Double-oy! When I added a family-room to my house here in Medford the lectrical inspector insisted that I install a duplex in EVERY wall at least 18" long, INCLUDING the one between adjoining (20" apart!) bathroom and basement doors!
There it was: chapter, verse and line. Somehow he didn't question the oh-so-bright 83802 dedicated lines streaking from the breaker box across the basement ceiling. But then the former only proves he may be wrong on the latter. Sigh....

Belden tech support replied to my email and said they recommend their FPLP cable (83802, 83803, etc.) not be used for 110v power supply, from panel to receptacle. They said it is for "Control and Instrumentation" cables for Fire Alarm and Tray applications and are not designed for 110v applications.

The assistant state electrical inspector and regional offices both said an emphatic "NO" when I asked if FPLP can be used in this manner. I have now contacted three electricians, the regional and state electrical inpectors offices, and Belden tech support. They all give the same answer.

I had hoped 83803, at least, could be approved but unless it was overlooked by the local inspector it would not be, not in my state. I was told I'd have to get it all removed at whatever phase of construction it was discovered. That could prove to be a very costly mistake.

Huh? But it's rated to 300v!
I wonder if the relatively tender Teflon outer jacket is the issue here? I cover it with a clear vinyl jacket for protection and a decent "hand" in my PCKits. It'd be a shame if one had to run it through conduit or another sleeve just for code-approval, as it probably works better with its minimal all-Teflon dielectric.
When you physically look at it compared to 12/2 or 12/3 Romex it's quite a surprise to hear that it's "not recommended". Certainly the vendors I've spoken with don't question its use at 120v....
Ican think of no better-sounding affordable cable for dedicated lines. It'd be a shame if potential users are disuaded from using it because of fear of having to snip it off at both ends if "discovered" by a hawkish inspector.
Very costly to remove? At least not in Massachusetts. Code requires that all "old work" be removed ONLY when discovered upon having full access, like when a floor or ceiling are ripped up and you see a few old cut up lines sitting there (as happened to me in my 1910 house).
NO-ONE to my knowledge has ever been asked to remove, or even disconnect, an 83802/3 line used for 120v.
I don't pretend to be an expert on codes and wire insulation classification. When you cut up the 8380x and look at its construction it seems awfully sensible to use for our audio power purposes. Since it's all-Teflon dielectric I know that it couldn't possibly be reponsible for starting a fire, so I'll take my chances, being pretty confident that a personal insurance adjuster could easily protect me from an aggressive company inspector if there's ever a catastrophe. I don't mean to be argumentative. I just want this excellent,very cost-effective product to be available to us. You couldn't design or make a better power cord for 5 times the price on a small scale....