Last night, former Google executive said on Twitter that he tried to get the Google engineers to treat underscores in the URLs as separators, just like how they used hyphens as separators in the URLs. He said it never happened, at least while he was at the company.

For the historical record, I did try to get Google to index _ as a separator so we’d process the web as it existed. But it wasn’t a high priority request, so it didn’t make it across the finish line. 🙁
— Matt Cutts (@mattcutts) December 1, 2017
This goes back to when in 2007 Matt Cutts posted on his blog about underscores vs hyphens, which of course we covered as did many other SEO blogs at that time. Now, Google says they don’t care – there is no difference, but I am not sure if that is 100% true or not.
That all being said, if you want to go back in histroy, check out this tweet from Anil Dash:

For years, @mattcutts was patient & wise as the most visible public ombudsman for Google. But what happened to the web (and to culture) when an entire industry started to obsess over every pronouncement from the company? Some necessary history here:
— Anil Dash (@anildash) December 1, 2017
Make me feel like the past 14 or so years have been a waste here. 🙂
Forum discussion at Twitter.