Just suppose you disavowed a link by uploading your disavow file. Even google warns that one should use the tool carefully which is logical, since it can do a lot of harm to ones ranking, it still is possible to upload disavow files again and again. Does anybody know for sure that google will count links again even though they have been disavowed once?
...it still is possible to upload disavow files again and again. Does anybody know for sure that google will count links again even though they have been disavowed once?
Q: I uploaded some good links. How can I undo uploading links by mistake?
A: To modify which links you would like to ignore, download the current file of disavowed links, change it to include only links you would like to ignore, and then re-upload the file. Please allow time for the new file to propagate through our crawling/indexing system, which can take several weeks.
This would seem to suggest that uploading the file again overwrites the previous set of disavow links. But, as stated in the blog post, this can take "several weeks". (Note, however, it can take "multiple weeks" for links to be ignored in the first place, since they "need to recrawl and reindex the URLs you disavowed before your disavowals go into effect".)
However, in the Matt Cutts video from the same blog post he does state (highlighting my own):
6:18 "Well, what if I want to undisavow a link, or reavow it?" And the answer is, "That will take even longer." So I would say, once you disavow a link, make sure that it's a link that you really want to disavow, that you don't want to have it count anymore, because it will take a lot longer, and we might not give it the same weight if we start to allow it to be reavowed.
Note that "even longer" and "a lot longer", I take to mean as "a lot longer [than multiple weeks]".
That sounds semi-permanent to me. The warnings are justified - don't expect to be able to reverse the process.
I think it's more likely Google ignores disavows unless they also think the link is spam. If you had no unnatural links to begin with, it would have no effect. Cyrus disavowed ALL links to his blog, yet it did not change rankings. Traffic only changed after an algorithm update, which would have lowered traffic anyway.
I believe Google is trying to make an educated guess about which links to disavow. If it is a good link, it ignores your request to prevent you from shooting yourself in the foot. Google's goal is to disincentivize spam. Since negative SEO is possible, Google aims to automatically determine whether to count a link or not. The disavow tool was probably added as a stopgap measure or at the request of a very important client when negative SEO was buzzing. They probably don't value its input as much.
Moz has a guide on the disavow tool.
You'll still need to wait for Google to recrawl all of the links on your disavow file though. John Mueller from Google has said that it can take up to a year for all of your links to get recrawled. However, in my experiments, the longest a link took to be disavowed was three months. Most links were disavowed within a month.
However, Matt Cutts commented earlier in the year that it takes much longer to reavow a link than to disavow it. You would think that the next time it was crawled, Google would remove the invisible "nofollow", however, there is some type of lag time built in before the link starts to count again. The purpose of this is to make it harder for spammers to find ways to cheat the system.