To do a full post-QC’ing, yes, but that doesn’t mean we cannot start. While we cannot today decide whether a future Bitcoin community will fork to freeze non-QC-safe coins, it seems likely they will (a Bitcoin with a few million extra coins is almost certainly value-ruining). Given this, we can start to move now - adding a hash-based signature opcode to tap script allows wallets to, today, transparently and for free, ensure their coins remain spendable in the face of such a future.

Fair. Starting is entirely sensible. But I would rather say 'planning' and researching, than starting.

Also: I feel that existing deployments on other systems are a bit different, where the stakes are not as high. Also: 'extra coins'? You're talking about stealing, not extra coins, right? (Academic? Maybe, but if we had done confidential transactions, would be v. different!)