This gave me flashbacks to my experiences at a couple of places, and I really feel for Coraline. These kinds of experiences seem to happen very disproportionately to minorities with strong opinions (aka folks who aren't just going to grin and take it) so naturally some of the comments here aren't surprising, until you've gone through it, none of it makes sense. So naturally most people will side with the company, thats just what happens.
For me, it was these random things that would come up very suddenly seemingly from out of nowhere. Some one would have 'complained' about something. The thing would be completely ridiculous, and my manager could never tell me exactly what I should have done to fix it, but it would be a problem. One time I was told I was "unavailable to my team", even though we had slack and nobody had tried to contact me and failed or had even gotten a delayed response.
In another situation I had been having problems with 2 specific team members (couldn't handle any kind of feedback that wasn't completely onboard with their amazing ideas), and in the same exact week, my boss said (and this is a quote) ... "the problem may be that you are TOO good at your job", I got a merit based raise (after just 6 months there), and at the end of the week I was put on a PIP and told I had "no future" at the company. Hows that for consistency and your manager working to help you. lol.
The part that is absolutely maddening though?
That same communication style that everyone acts like is a huge problem. Some people get to talk like that to anyone at anytime in pretty much the same way in the same company you're at ... direct, pointed and directly opposed to some idea, sometimes even rudely. But when you do it as a minority (sans the rudeness), its a problem. I remember one Engineer, losing his shit because our company had decided to pay for only part of our parking in our new downtown location. He raised his voice, and he cussed in addressing a SENIOR FEMALE HR executive that was seated in the meeting, full of people. Nothing happened to him. If I'd tried something like that, I'd have been out of there in 1 week flat. That's the kind of double standard you have to just accept as a minority in tech, and I think its absolute trash.
Long story short, this stuff is real, it happens and its absolutely bullshit. It makes you feel like you are going batshit CRAZY (I'm an athlete, and at one point during one of these being-managed-out episodes, my blood pressure hit 140. thats hypertensive) ... and like I've alluded to before, I wouldn't be shocked if something like this played a role in that Uber engineer's suicide a few months back, because it can really wreak havoc with your mental state and sense of self if you don't have a good support system and/or therapist.
The key is to remember, you're not perfect, be humble and fix what you can, but also remember that lots of people and companies are full of shit, and quite often (especially if you're from a minority group in tech), its not you, its them that are fucked up, despite people on HN doubting your every move and intention.
Also always find a manager that will take a bullet for you, and if you're put on a PIP and you know its bullshit, just leave, don't suffer the indignity and mental anguish of getting shit on for weeks, all the way to a crappy severance if you can help it.
Cheers and Good Luck Coraline!