This seems like the most viable option for non-forum-based feedback that I've heard yet.
Another possibility, and one which might be easier on the SC database, would be to allow people to use the site to send e-mail to a user's registered address, without actually giving out that address if the user doesn't want it revealed. It would probably be best to give users the option to disallow this for their accounts, though, so the feature can't be used to spam anyone.
On the other hand, it's hard to imagine how much these features would add that can't already be expressed by simply adding someone to your favorites list, or contacting them via whatever contact info they've chosen to reveal.
One other idea which I mentioned a while ago in the IRC channel is allowing users to attach a simple "I liked this" flag to specific comics. Whether the name of the user who attached the flag should be revealed, or whether users should be able to see such flags that are attached to others' comics, I don't know.
I'm still reluctant to suggest bringing back the old voting system, although it is possible that the lists now presented on the new front page would encourage more people to vote more frequently.
And I'm definitely opposed to publicly viewable comments attached to individual comics.
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The what mentioned above is total fiction. Please don't take it seriously!