It seems like the result of this is to cycle, with a decrease in difficulty resulting in a following increase in difficulty and then an increase in difficulty resulting in a decrease in difficulty. This is meta-stable: it's not a system that converges on a single value, but it's a system that oscillates between overshooting and undershooting the true value.
Plenty of systems work fine like this in nature - it's pretty much a textbook predator/prey dynamic, and yet carnivorous life has been going on for several hundred million years on Earth. It would be a problem if the dynamic was for the number of miners to drop to zero or explode to infinity instead, but this is a negative-feedback cycle, not a positive-feedback one.
It's not meta-stable because if there is a difficulty above which mining is not profitable then the oscillations will become larger and larger until eventually it is too expensive to complete the next difficult adjustment period. The easy adjustment periods will become shorter and shorter.
You are wrong as characterising this as negative-feedback, this is positive feedback because if you are presented with a situation where in even "weeks" (which now last 6 days) the difficulty is 10% less than odd weeks (which now last 8 days), then you will join mining only the easy weeks which further feedsback to more distortion.
edit to add: I realise the adjustment period is not aimed to be 7 days, this is for easier illustration.
Interesting. It seems like a classic "tragedy of the commons" situation. Even if miners want to see Bitcoin succeed (in order to get a return on their mining hardware investment), at some point they have to join the alternating adjustment period schedule to remain profitable, making the problem worse, and riding the sinking ship down...
The question is what is the "activation energy" required to initiate the oscillations. Is a large miner (how large?) likely to attempt this knowing the ultimate outcome?
And more importantly, can it be fixed? The protocol isn't set in stone.
Plenty of systems work fine like this in nature - it's pretty much a textbook predator/prey dynamic, and yet carnivorous life has been going on for several hundred million years on Earth. It would be a problem if the dynamic was for the number of miners to drop to zero or explode to infinity instead, but this is a negative-feedback cycle, not a positive-feedback one.