SOME interactions between new and old clients POSSIBLE
What are you saying isn't possible? Did you suddenly lose functionality when CLTV was released?
but will be left passing the parcel of unknown content
No they won't-- but even if they were, why would that be bad?
95% consensus
95% of what? and where are you getting that figure from? The code in the Bitcoin classic repository doesn't appear to attempt to do that.
when 95% of people are happy
Oh, of people? How the heck do you intend to measure that? ... if we could measure that we likely wouldn't need the blockchain.
So what's the difference between a hard fork and a contentious hard fork?
Non-contentious hard forks (historically) addressed some outstanding issue that threatened Bitcoin's functionality. IE, they fixed something that was indisputably broken.
Contentious hard forks seek to fix or improve what "isn't broken" from the perspective of some non-negligible faction of the socioeconomic majority.
Block size is the perfect example of this. It pits the 'payment network' vs the 'store of value' clans.
Fortunately for the small block militia, Bitcoin was designed to protect minority opinions from the tyranny of the majority, by giving them nigh-infinite veto power.
Another way to say "contentious hard fork" is "breaking Bitcoin." They are functional equivalents, and equally impossible AFAIK.
Bitcoin was engineered to withstand a continuous, coordinated attack by all the world's nation states, banks, and hax0rz. It's not going to change just because some Gavinista-cum-Toominista assclowns make a lot of noise on Reddit about "Capacity Cliff" and "Hard Landing" FUD.
The "Free transactions 4eva" dimwits never had one iota of a chance in hell of perturbing Honey Badger.
The funniest thing is they know that, but refuse to accept it.