I've never set this up because
reasons. (i.e., I hate this plugin in KOReader with a fiery passion, because it's a giant PITA to maintain the pile of hacks necessary to make it somewhat user-friendly, which, case in point: it isn't

).
I assume I did quickly check that the patch worked at one point, though ;D (EDIT: Yup, I've got an old authorized_keys in there, so, at least, that looks right. I can't vouch for your kchain alias, but I don't have any issues with a pam_ssh and/or keychain @ login workflow over here. Double-check that you actually have an ssh-agent running with the right key loaded? (
ssh-add -l)).
As usual in this situation, try running your client session with
-vvvv, as well as checking the server logs (via
logread), that may shed some light on the issue.
EDITē: And, no, AFAICT, the "SSH public key" field/button/whatever being visible has no bearing on your actual setup, it's always there.