Planet13 - 2:06 pm on Aug 11, 2013 (gmt 0)
"If it's the randomized response it would suggest that I don't change the content back since that would be trying to please Google, but how long does it last? It's been 8 months. What would you try, if anything, at this point?"
You said you did this on a couple of pages, right?
It might be a good idea to experiment and change one or two of them back and see if it makes a difference.
I personally think that it is more likely some sort of over optimization penalty.
Wikiepedia pages get content added all the time.
Pages that allow comments get content added all the time.
Ecommerce category-level pages get new products added and old products deleted all the time.
Event pages get content added and removed all the time.
So is there some classifier that google uses to denote certain pages / certain sites as being "evergreen" and those sites are not allowed to update their content?
Aside from the thought that the content may have tripped some over optimization penalty, how UNIQUE was the content that you added?
Is it possible it was more of a Panda effect than a pure OOP?
Getting back to changing the pages back or not; I would possibly experiment, depending on how many pages you changed.
I would possibly change one or two back to how they originally were, and maybe 301 one of the pages with the additional text to a new URL. I would probably also try to keep the same new text on one page but try to deoptimize it a bit for its keyword.
I don't really know how much there is to gain from waiting it out and in today's google world, I think we have to take chances and experiment - hopefully not on our main sites but on sites or pages that don't rank as well as we hope.
Hope this helps.