Just a quick bit of information here on what I have recently checked. I was faced with proofreading a paper that included information about online training. Of course, the Internet featured heavily in the text. But the authors had written it as internet, although I had almost always seen the word capitalized. So I went on the search. Here is the most useful website that I found on the topic. I then, of course, started to philosophize on how long that search would have taken me in the pre-Internet days – but then, of course, I wouldn’t have had to look up the word Internet.
In my proofreading, I will continue to accept both, that is as long as the author has remained consistent!