This author is in his own little bubble and doesn't understand the vast amount of blog-repost spam that google has to deal with. The way their algorithm most likely deals with this is a mixture of domain rank + tenure... how long has this copy of this article existed on this domain, and can we be sure this is the original copy?
The author says the article was removed in 2006 ("[...] posts, were not accessible anymore") and then he re-posted the article at a new domain in 2013. That means any copy/crawl/repost of the article from 2006-2012 is now the oldest living, and thus "original", version of the article. His 2013 repost was seen as just another blog-spam copy.
Google is not forgetting the old web unless we see evidence of content disappearing from the index that have been consistently hosted at the same domain & URL since their original posts. Unless you properly 301 your URLs to new locations and consistently host your content, it's a guessing game for the crawler to determine where the original content has moved to.
The author says the article was removed in 2006 ("[...] posts, were not accessible anymore") and then he re-posted the article at a new domain in 2013. That means any copy/crawl/repost of the article from 2006-2012 is now the oldest living, and thus "original", version of the article. His 2013 repost was seen as just another blog-spam copy.
Google is not forgetting the old web unless we see evidence of content disappearing from the index that have been consistently hosted at the same domain & URL since their original posts. Unless you properly 301 your URLs to new locations and consistently host your content, it's a guessing game for the crawler to determine where the original content has moved to.