> Yubikeys are great for security, but not when you leave them in your computer unattended. At that point, anyone can take the key and use it for 2-factor authentication/SSH/GPG signing, so it’s not much better than just using a normal password.
Even after the edit at the top regarding PIN it still seems to not get the main point of a U2F token: It's physical. It's incredibly hard to extract secrets from it. It's local to where it physically is.
If I have a password then there are probably a couple of services and people that could reasonably get to it either by hacking the service the password unlocks (in storage if its a really insecure service or in transit the next time I log on), or can extract it from my password manager/memory/browser or whatever.
The point of a U2F token for me is to change the number of people who can reasonably authenticate as me from "everyone who has my password" to "everyone who have a physical key I keep within a reasonable distance from me that is incredibly hard to copy and has my password". U2F also validates auth origins quite a lot better than many other methods, although I guess that is not relevant to this argument.
A hardware U2F token is not the end-all be-all security, but it reduces potential attackers a lot.