ColourOfSpring - 8:22 am on Jun 1, 2013 (gmt 0)
Candidly, no. My quote (on Google's quotes) implies if your website was "that good"... you wouldn't need Google to do anything because someone else was delivering you ill will... as the ill will wouldn't work. At worse, you would see a temporary gain and a lose of that gain... nothing more. At best, you would get the gain and never lose it. If you are not responsible for the off-page signals those signals generally didn't produce your stable ranks.
The existence of unnatural links penalties proves beyond any shadow of a doubt that Google can penalise inbound links (whether you placed these links or not yourself). There is no such thing as a "slight rise, slight fall" when your site is penalised for unnatural links. The question REALLY is : do Google always notify us when they penalise us for links pointing to our site? We can never know that, but we can observe.
With Penguin, there can be occasions when people observe "slight falls", but there are also many instances when falls are significant and even appear arbitrary - with 3 or 4 unconnected sites that were top 10 all appearing on page 5 together - the symptoms of a penalty. Of course, Penguin is likely to be more than merely looking at links, but from most people's observations, Penguin is very much a filter that concentrates largely on your link profile.
These types of penalties do not really take into account the quality of a site i.e. quality in the eyes of a human being - these types of sites would (or should) benefit from a manual review by Google that considered quality guidelines - at the end of the day, if a site has a high conversion rate, it means the visitors have largely approved it, and so should Google acknowledge the site is a lot better than the algo deems it.