Have you ever considered using ScrapeBox or Xrumer for consistently building backlinks over a period of time? A short burst of backlinks and then nada allegedly looks suspicious to Google.
So, comment spam tools? That's deep into the realm of "black-hat SEO".
That it is. BH SEO is (unfortunately) extremely effective.
If you're content farming by rewriting other people's content, you're not providing much additional value to the Internet at large and you're, at most, a few steps away from being a black hat as it is.