FIDO can't force any app developers to do anything but fwiw I think "pressuring" people to encrypt secrets at rest rather than storing them in plaintext is ok.
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There's levels to appropriate paranoia around these things of course. SSH private keys are stored in plaintext for millions of engineers around the world - sometimes probably even passed around through unsecured emails or whatnot I would guess. They're still largely more secure than user:pass on aggregate, despite that rather major peril.
So ultimately, plaintext creds are not necessarily catastrophic. But still - imo - something worth concerted effort to dissuade at least at early stages of standards' implementation.
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Edit: also, looks like the outcome of that thread was ultimately that KeepassXC have opted to implement the spec as per[0]. Good outcome to a good request.
[0] https://github.com/keepassxreboot/keepassxc/issues/11363