I believe those policies exist. I don't believe they are followed by everyone, and all it takes is a vocal minority. I've seen plenty of comments on HN from people who say something like, "Hey, I'm an employee of X, this is my own opinion, but..."
I regularly am discussing Google's business with Googlers on here. Some of them disclose in the post, some of them disclose on their HN profile. Many do not, and calling them on it is generally discouraged, but it's usually not super hard to figure out or prove.
There are definitely some acting as spokespeople (even if they claim otherwise), but there are also quite a few who are just, you know, incredibly biased fans of their employer, who like to defend them on topics unrelated to their job.
But when a tech company has 100,000 employees, it's not particularly surprising to see a good number of them on a tech forum. ;)
Or that they start every comment with 'I'm an employee of X'
They might just say, 'That seems silly!', 'You're a nut', 'Do you have a source other than yourself'. Or they might just downvote stories that have a negative effect on their income.
You've got 100k people working at google and many of them are going to be active on this type of forum. The same goes for the other big guys that have a ton of employees
There are regular comments by declared employees of quite a few companies including Google on HN. The commenting and vote/flag brigadeering around subjects that center on one of these companies is such that many subjects are either voted off the homepage entirely or the participants in the thread get downvoted/upvoted to better support the company position or narrative.
Whatever else it is, it's one of the more important guidelines of the site (at least judging from the time Dan and Scott spend on it) that you not make appeals like this in public comment threads. What evidence you hsve of this, you should send to hn@yc.
How is that evidence of "vote/flag brigadeering around subjects that center on one of these companies [...]" by those people? This story sat on the front page for a day, has zillions of votes and comments and as far as I can tell, even people who work in the field can't actually figure out what it's about.