I just found out that someone already wrote a YouTube comment downloader.https://github.com/egbertbouman/youtube ... downloader
However, for Yahoo! News comments, DailyMail comments and Disqus comments, I have to write the code myself.
I am very upset that Gawker has deleted years of comments on its website when it was shut down. They archived the articles, but not the comments. However, the comments are far more valuable than the articles themselves.
There's a high risk that Yahoo! will delete the Yahoo! News comments and Yahoo! Answers because it has been recently acquired by Verizon.