Again, in case you are still blind to the moral principle, the only person who has a legitimate claim on managing the risk is the owner of the coins themselves. Any lesser standard is simply theft.
I'm sensitive to accusations of lacking moral principle, so let me take one more stab at this. Let's say I'm the Grand Overlord of Bitcoin, with unilateral power to act, and I'm faced with this situation.
If I do nothing, the abandoned coins are stolen.
That does not justify you stealing them before the other party can steal them.
But abandoned coins have no worth to their owner anyway, so the owner is not losing anything.
Up until the very instant they are stolen, the owner has potential value. The exact instant some other actor might steal them is literally un-knowable. Ergo, at the instant you (either a single Bitcoin Overlord or the collective) steal them, it was at a point in time that the coins had potential value to the rightful owner.
The thieves gain,
I'm with with you so far....
and all law-abiding bitcoin owners suffer from dilution of the market
...nope. Lost me. Wait - not 'lost me' - you are
wrong. There is no dilution - those coins already existed. Their potential value may at any time up until the theft may be converted to actual value by the rightful owner.
with the stolen coins and the loss of confidence in bitcoin.
The loss of confidence due to the ability to crack an obsolete format key pales in significance to the loss of confidence in bitcoin due to the manifest will for the collective to change the rules to invalidate keys.
Outcome: failure of moral principle,
Bullshit. It is never moral to steal, even though the objective be to prevent some other from stealing.
as law-abiding people suffer, while lawbreakers gain.
The law abiding suffer no loss. That other thief may gain, sure. But what of the rightful owner? Again, you have no means of determining exactly when that other thief will act. The management of the risk of such theft is
solely the prerogative of the rightful coin owner.
Obviously, this all hinges on the degree to which efforts are made to reach everyone and get them to take the necessary action. It would be a failure of moral principle to do less than the utmost in reaching out to everyone and accommodating them as well as possible in assisting them with acting to safeguard their coins. For this, the elements of time, maximum communication/broadcasting through all available venues, and clarity of the warning would be critical.
Necessary yet insufficient.