Yes ;) The pages did rank (and were indexed) and now they don't rank - and are not indexed.
- on a side note, the corresponding pages for the BlueWidgets where comment language = content language are enjoying a much higher/better indexation than before.
Yes... currently working on it, but there are a lot of pages, and 'generating' unique content won't work. Experimenting with a language-detection software to only show comments/reviews for the relevant language.
What I have seen is that it primarily affects pages where there is a substantial amount of 'foreign' language elements in one or more large blocks in the same language.
If you have a few short comments, then you shouldn't be affected.
However, to be safe I would do some checks to make sure that you have at a bear minimum 60-65% of 'correct' language content on the page.
Again, I only noticed this because all of the pages from the website are not yet indexed. Now google has started skewing and not indexing pages google probably finds "not relevant to index". I would insofar then not say that it is a penalty... but it might as well have been for what it is doing to my traffic since a lot of important long-tail pages are no longer indexed.