Sounds like you see me as an untrustworthy source, so all I can suggest is that you look into this yourself. Search for "--" in pre-LLM forum postings and see how many hits you get.
As I was in the process of typing the search term to get my comments (and had just typed 'author'), this happened to come up as the top search result for Comments by Date for Feb 1st 2000 > Dec 12th 2019: https://news.ycombinator.com/item?id=21768030
Note that I wasn't searching directly for the double hyphen, which doesn't seem to work -- the first result just happened to contain one. If I'm covering for the Anthropic guy, I could be lying about the process by which I found that comment, but I think you should at least see this as sufficient reason to question your assumptions and do some searches of your own.
I've just realised I messed up the search, and the algolia link is to my pre-2020 comments containing the word 'author'. But my full (far longer) list of pre-2020 comments also shows some pretty heavy double-hyphen use: 6 hits on page 1 of the results, 15 hits on page 2, and so on.
Here are my pre-2020 HN comments, with 3 double hyphens in 8 comments: https://hn.algolia.com/?dateEnd=1576108800&dateRange=custom&...
As I was in the process of typing the search term to get my comments (and had just typed 'author'), this happened to come up as the top search result for Comments by Date for Feb 1st 2000 > Dec 12th 2019: https://news.ycombinator.com/item?id=21768030
Note that I wasn't searching directly for the double hyphen, which doesn't seem to work -- the first result just happened to contain one. If I'm covering for the Anthropic guy, I could be lying about the process by which I found that comment, but I think you should at least see this as sufficient reason to question your assumptions and do some searches of your own.