aristotle - 10:10 am on Oct 9, 2012 (gmt 0)
a devaluation of low-quality backlinks that cause small ranking losses.
Hmmm - why do you think that would that need to be part of Penguin when it's already something Google does anyway? I'm not saying it isn't, mind you, but it would be kind of a "double indemnity" thing, right?
I was sloppy in how I stated it. Rather than "low-quality" backlinks, I think it was actually a devaluation of backlinks that appeared to be purchased or artificially built, particularly those with anchor text containing keywords. The reason I associate it with Penguin is because the effects on my two Penguinized sites appeared on April 24, which was confirmed by Google as the date of the original Penguin rollout.
Whitey - You're right. I probably should have included onsite factors, particularly signs of over-optimization, as an aspect of Penguin.
I did that whole post hurriedly and sloppily, and should have been more careful and thoughtful.