Chain reorgs and double spends are two different sets. IIRC the 2010 reorg didn't have any double spends

>It’s impossible to count how many of those abandoned transactions were successfully replayed on the new chain

To detect if transactions were double spent, you would need some sort of database. Like a data base with _really_ good integrity. Maybe with periodic and limited deltas. Increase the some of the integrity with decentralized time stamping, sleeping-beauty hashed chaining. hmmm I wonder if there is anything like that...

Cheekiness aside, it's possible a node could ascertain whether or not transactions were replayed and definitely not impossible. The steel-man reply is: node software doesn't have great resources to do it.

No, it's literally impossible. That's the whole point of a decentralized blockchain: nodes cannot (and don't want to) have total information about the network. That is, nodes don't know if re-org's are happening elsewhere in the network and don't know if they are about to get re-org'd. Every re-org is an opportunity for the actors involved in the re-org to send BTC elsewhere on the new chain and thus make transactions on the old chain "reversed".

Nodes in Bitcoin do not care if these transactions were reversed across chains, they only care about the transactions on the one most work valid chain, where "valid" is a set of rules expressed in the software binary that node is running. Two nodes can disagree on validity rules and literally never find out. Or a block can trigger a fork in the 2 nodes and then we need developers to tell us which chain is valid Bitcoin (see 2017 fork). While this is happening, transactions can go from being settled in a valid most-work chain to suddenly being considered invalid because everyone else is rejecting that chain.

It's a faulty design for a global payment network. We'd expect it to be predictable in how it handles transaction reversal and for human entities to be held accountable for ruleset changes.

You've moved goalposts. Your original claim was:

A) >It’s impossible to count how many of those abandoned transactions were successfully replayed on the new chain

now it's

B) >nodes don't know if re-org's are happening elsewhere in the network

Claim A is false as it is indeed entirely possible:

I have a chain of height 100. It is fully synced. I am sent a series of blocks diverging at height 80. I have all the information I need to ascertain which of the transactions in the two competing chains are being replayed or have been doublespent.

Claim B is true

You're assuming in claim A that your node knows about all abandoned chains. Like I said, that's impossible because nodes don't have total information. I'll simplify and strengthen my claim for you: it's impossible to find all reversed transactions.

The comment I was replying to claimed that transactions can never be reversed. I'm just highlighting how this represents a poor understanding of how Bitcoin really works.

Forks aren't abandonment. And at this point, the market determines which chains are abandoned, it's not a single actor that has any sort of control.

That is like saying that there are no back doors in open source software because anyone can have a look at the source.

'The market' is a handful of powerful miners anyway. As if your 1 vote could do anything about some fork abandonment or whatever. Also, do you monitor the whole network constantly? You have to sleep at some point. You know who does constantly monitor the flow of currency to a somewhat trustworthy degree? Banks and governments do.

First of all, you seem to be addressing bitcoin in isolation and not crypto in general. What forces do you think make Bitcoin worth more than ETH or more than Bitcoin Cash? Market forces. Supply and demand. Just like all commodities. These are invisible hand forces that no single person controls at this point. Even if there are varying levels of centralization in the chains themselves, the market decides whether to back ETH or ETC or some mix of both. So, like any decentralized system, the network is monitored in a decentralized manner. The chains themselves have solved for consensus problems. That's the whole thing keeping blockchains going. No, banks don't constantly monitor everything (although admittedly, it's more than ever thanks to technology). Large amounts of cash still flow around the globe. And whether your government is trustworthy depends largely on which of the 195 nations you live in.

The worth of a cryptocurrency is a bit of a weird thing to me since the decision where the decimal point is arbitrary, the different cryptocurrencies aren't that different in value, they just use different decimal points. If ETH decided to shift the decimal point by two digits, it would suddenly be twice as much "worth" as bitcoin.

If a company issued twice as much stock, would it have a market cap that's twice as high as it's 1x issuance? If Amazon offers 100 AWS-Bux for every euro/yen/dollar would they bring in 10x as much revenue if they offered 1000 AWS-Bux for every euro/yen/dollar[1]? No, to suggest otherwise would be economic delusion; economic literacy doesn't seem to be the ETH's community's forte.

The quantity is irrelevant, the exchange rate that reaches equilibrium is what is relevant

[1] There are marginal second order effects with human psychology (people feeling like they got more of something)/ brokerage arrangements (1 share being the smallest divisible portion of ownership that a SE will clear causing share subdivisions needed to be cleared by a broker)

Companies issue more stock all the time and it definitely has some impact on the market as it devalues a single share.

If a company simply turned each share into two shares, then the market cap would be the same but the fractions of the markteshare that can be traded are smaller.

If the company suddenly issued the entire stock on the market again, the price would plummet to half.

You don't have to monitor constantly, just some time after you make a transaction. Long chain reversals grow exponentially unlikely the longer the chain gets.

In practice, this does not seem like a large problem.