Google will devalue any web pages that permit comment spam. Once they devalue those pages they will pass no link juice. The websites that permit that webspam will suffer in rankings, and in certain egregious cases, they will be de-indexed for allowing that webspam to pollute the World Wide Web.
As Web spammers escalate their vicious attacks on unsuspecting bloggers you will likely see an all-out war on web spammers. Their activity is being documented and it will become part of their permanent reputation, impossible to erase. Web spammers may at some point have to change their names and hide their past identity to ever hope to regain any respectability.
I got this stuff from Sergey Brin and Larry Page, perhaps you have heard of them? They first introduced this capability to the public in the original Backrub White Paper.
When you read this document you will understand that “sites” don’t pass link juice, PR isn’t assigned to “sites”, it is assigned to individual web documents. So a website may have web pages that pass link juice, while at the same time, other pages on the same site may not.
Google refers to this ranking factor as Trust, they assign a Trust value to each page that is indexed and the amount of link juice that is passed is weighted by this Trust value. As a web page accumulates spam, as detected by Google, it lowers the Trust value for that page. A page with zero Trust will pass zero PageRank.
The exact method of measuring this Trust value, and the weighting factor algorithm, are among the most closely guarded secrets of all search engines.
I stand corrected, I should have said they devalue links from any pages where Google detects spam. It is certainly possible that you can have spam that goes undetected for a period of time, perhaps to never be detected.
You still seem to struggle with fundamental concepts like “PR is assigned to individual pages, not websites.” When a page’s Trust is devalued due to spam it doesn’t cause a sitewide penalty, yet you seem to be inferring that I somehow made that assertion, I did not. It looks to be yet another one of you straw man arguments that you have become infamous for on this board.
Let’s just agree to disagree. I believe that Google does, in fact, devalue pages that contain excessive spam. If you want to go on record as having the opposite opinion, then so be it. I’m not here to prove you wrong, the truth will find away.