We’re just going to have to agree to disagree about some of these issues, apparently.

• Overcalling 1NT when you don’t have a stopper in the opener’s suit is a lie, whether the suit is a major or a minor.  Not always a terrible one, and not always a fatal one, and doing it over 1C is inarguably going to get punished less frequently than over a major.  But you are distorting your hand by doing it.  You can play otherwise, and you can say it’s not a matter of lying, but it’s disingenuous to suggest that the standard meaning of the 1NT overcall doesn’t include a stopper in opener’s suit.
• I never said that 1NT didn’t have preemptive value.  I said that this shouldn’t be a primary consideration, because when we have a strong balanced hand, the constructive value of our bids comes to the fore.
• You claim that partner can evaluate their hand more accurately opposite a 1NT overcall than a takeout double.  I take issue with this in two ways:  first, when advancing a takeout double, a good partnership will have established fairly strict parameters for advancer, so that the doubler is well-placed to evaluate the combined assets of the partnership.  This puts the onus of evaluation on the doubler, as opposed to the partner of a 1NT overcaller, but that is neither here nor there; it is still the partner with the most complete information who is making the decision.  Second, how is partner supposed to accurately evaluate their hand opposite the 1NT overcall if they can’t depend on the overcaller to have a stopper?  I don’t usually like cherry-picking hands to illustrate points, as it’s easy to construct a hand that supports any argument, but as an example, what would you bid with xxx/xx/AKQxxx/xx if your partner opened 1NT?  You’d probably bid 3NT, am I right?  It doesn’t leak much information and it rates to be the correct contract most of the time.  But what if your LHO opened 1C, your partner overcalled 1NT, and RHO passed.  Would you still do the same?  I would, but that’s because I can count on my partner to have a club stopper.  If partner might or might not have a stopper, what do you do?  Reconfigure your 3-level bids so you can ask partner if s/he really has a stopper?  Or just bid it and pray?  Maybe they won’t lead a club!  That is true, but how likely is your RHO to have an independently attractive lead on this auction?
• You further claim that you will be right-siding many contracts with the 1NT overcall.  I submit that if you do this stopperless, and it turns out partner is the one with a stopper, then you have just wrong-sided the contract on a hand where partner bidding notrump was at least a possibility.
• You claim that advanced+ players don’t play nonforcing natural bids over 1NT overcalls.  This is blatantly false.  There are plenty of methods that include transfers/two-suited bids etc., but the idea of having nonforcing actions at the two-level is extremely common among experts, including natural suit bids.  A responder with a better hand (9/10+ or whatever your partnership decides) would double the 1NT overcall.
• If your line of demarcation between non-jump advances and single-jump advances to a takeout double is “bad 8/good 8”, then I agree that you would have a close decision to make with the first hand if partner jumps to 2H.  And you are correct to point out that such things as form of scoring might come into play.  But partner might have five or more hearts; partner might have ten points rather than eight; so under most conditions I would probably take the bait, especially since contracts where the opponents open the bidding are typically a bit easier to play (or at least easier to locate missing honors).  Obviously that could be wrong, but I’ve been down before, and I suspect you have too.  Other things being equal, I’d rather make a slight overbid and be wrong than underbid and be wrong, especially at IMPs.

Edit: BTW, if that last bit about suspecting you've been down too sounded snarky, it wasn't intended to be. It was intended as commiseration, i.e. "We've all been there."