As of today "centr E" is here mostly to make statistics of "crime prevention" by convicting random people on VK reposting "politically incorrect" jokes or memes. I don't think there's many forms of expression, including open letters or poems, left that weren't at least once classified as "extremism" in Russia...
https://web.archive.org/web/20141030004457/http://zapretno.info/?page_id=462