It absolutely is! It was widely discussed as such at the time, here is a thread where people ask how to vote and the operator of Eclipse said he was removing his vote for P2SH:

https://bitcointalk.org/index.php?topic=60937.0

You might not feel it's a particularly fair or representative vote, but it's still miners saying "I support enforcement of this new rule" or "I do not support this" where the majority of cast votes wins. Some miners have more votes than others, but it's still a vote.

 

Miners are trusted parties, they are just not all trusted simultaneously. Bitcoin can tolerate a small number of dishonest miners whilst producing a degraded service. It cannot work if all miners are dishonest or decide to deviate from their intended operation, like if they all produce empty blocks. The white paper made this clear from the start, and it's also common sense.

Allowing the majority of honest miners to keep the dishonest ones in check is what Bitcoin is all about. I don't understand this view that a very small change to the existing protocol is somehow terrible or impossible, but expecting everyone to simply build an entirely new system from scratch is easy and inevitable. I'd much prefer to just keep the existing system working as well as it has so far, and I think that is true of most users too.

 

No, coinbases are deletable. If some miners fork the chain and build a longer one, the others will all switch to it and the coinbases blocks they previously mined will never become spendable (effectively they were "deleted" before maturity). Only if the other miners also blacklist the majorities fork and never join it, then the majority for some reason gives up and rejoins the minority, is what you described correct. But why would they do that? If they're the majority then all the other nodes will follow them. They have no incentive to throw away their fork and rejoin the minority chain ever again.

I think the root of this disagreement is whether the block chain algorithm left by Satoshi is somehow immutable and itself the end, or whether it's (as I see it) just a means to an end and therefore an algorithm that can be tweaked and improved, to get us closer to the goal.

If the end is a useful payments system, as decentralised as possible, that prevents double spending, then this proposal is a simple enhancement of the current system that ensures corrupt miners don't get paid by honest users for services they didn't provide, thus discouraging a particular kind of attack.