Unspent outputs at the time of the fork can be spent once on each new chain. Mass confusion.
No, this is actually great insurance for Bitcoin users. Practically it says that if you get Bitcoins now and Bitcoin later forks, you will have your Bitcoins in each and every individual fork. You can never "lose" your Bitcoins for being "on the wrong side" of the fork, because you'll be on all sides.
This incidentally also offers a very efficient market mechanism for handling the issue: people will probably be interested in selling fork-x Bitcoins they own to buy more fork-y Bitcoins if they believe fork-y is good or fork-x bad. This imbalance of offer/demand will quickly bring the respective price ratios into a position where continuing the "bad" fork is economically unfeasible (sure, miners could continue mining forever from a technical standpoint, but in reality people with infinite bank accounts are rare).
Without a sharp constraint on the maximum blocksize there is currently _no_ rational reason to believe that Bitcoin would be secure at all once the subsidy goes down.
Bitcoin is valuable because of scarcity. One of the important scarcities is the limited supply of coins, another is the limited supply of block-space: Limited blockspace creates a market for transaction fees, the fees fund the mining needed to make the chain robust against hostile reorganization.
This is actually true.
(And the worst thing that can possibly happen to a distributed consensus system is that fails to achieve consensus. A substantial persistently forked network is the worst possible failure mode for Bitcoin: Spend all your own coins twice! No hardfork can be tolerated that wouldn't result in an thoroughly dominant chain with near certain probability)
This is significantly overstated.
Surely from an "I want to be THE BITCOIN DEV!!!" perspective that scenario is the very avatar of complete and unmitigated disaster. The fact is however that most everyone currently propping their ego and answering the overwhelming "what is your point in this world and what are you doing with your life" existentialist questions with "I r Bitcoin Dev herp" will be out before the decade is out, and that includes you. Whether Bitcoin forks persistently or not, you still won't be "in charge" for very much longer.
Knowing that I guess you can view the matter a little closer to what it is: who cares? People do whatever they want. If they want eight different Bitcoin forks, more power to them. It will be even more decentralized that way, it will be even more difficult for "government" to "stop it" - heck, it'd be even impossible to know what the fuck anyone's talking about anymore. That failure mode of horror can very well be a survival mode of greatness, in the end. Who knows? Not me. Not you either, for that matter.
Its important to distinguish Bitcoin the currency and Bitcoin the payment network. The currency is worthwhile because of the highly trustworth extreme decentralization which we only know how to create through a highly distributed and decentralized public blockchain. But the properties of the blockchain that make it a good basis for a ultimately trustworthy worldwide currency do _not_ make it a good payment network. Bitcoin is only as much of a payment network as it must be in order to be a currency and in order to integrate other payment networks.
This is also very true. Bitcoin is not a payment network any more than a girl that went to Stanford and graduated top of her class is a cook: for that limited interval where she's stuck with it. Course I've been saying that for a year now and pretty much everyone just glazes over and goes into derpmode. I guess it's a distinction whose time has not yet come or something.