I do not have a subscription to view the quote or the messages you referenced (#2-7) that made sense to you. But linkbacks does concern me for one reason.
The reason being is that one link next to your results at Google labled similar pages which will display what Google feels are pages that are relative to that result. Oft times you will find interesting results with the related:domain.com query at Google, in that there are a variety of items in that result set that are not quite related.
Although I have not seen any evidence of those non-related items being of an adult nature, I have seen results that included such as gaming, casino, hotel chains, etc.
It could be because of Google's ability to filter for Adult content that what GoogleGuy says may be correct -- not to worry about Adult sites linking to you. I can agree with that part of it. But on the other hand, I do not take this to mean that you do not have to worry about other types of sites linking to you.
The unknown in this scenario is how much weight does Google put on any given linkback. That would probably depend on many factors of where that linkback is and what all is in and around it.
In a nutshell, I feel that linkbacks do have an influence in some way. But in the overall scheme of things, it is just another factor in Google's complexity of other factors all intermingling together that makes it difficult to understand how much influence it really does have.
