> If I authenticated with my junk key, would my other keys still be at risk? Yes, if you authenticate with your junk key (or no key), and SSH agent forwarding

> If I authenticated with my junk key, would my other keys still be at risk? Yes, if you authenticate with your junk key (or no key), and SSH agent forwarding is enabled, you are still at risk. It lets the remote machine login to any server with any keys that are on your local SSH agent. Parent's link shows how this can be abused. Fortunately, it's disabled by default, at least on newer versions.