Does the author really expect people to log in to instagram in order to see a post he is sharing? I don't get why the author wasn't able to screenshot the post.

My personal opinion is that concealed filming in public should be illegal. Open filming should be courteous, and if someone requests they not be filmed (and they’re not a public figure/government employee), the filmer should honor that.

Otherwise, I see no problem with it, and I’ve been filmed in public a LOT.

Its always OK to film the police (and other public servants)

If they're allowed to film us with security cameras every 10 feet, we shouldn't make criminals out of people using their phones to film in public or semi-public (like a grocery store) places.

In Germany there are laws in place which forbid filming or taking pictures of others without their consent. It's called the "Right to your own picture". There are exceptions, for example when you take a picture of a famous building with hundreds of people in front of it.

ITT people quoting US law as a universal ethical standard

legal ≠ ethical

Get outta here with your "no expectation of privacy in public", that's a legal concept and has nothing to do with the question. Moreover, that's only the law in the US, not everywhere

Yes, it's in the public. Don't expect privacy.

Yes. If you're on public property, filming is fair game unless you're harassing a person.

I've asked a Dutch police officer and she said I can record someone if I feel threatened, and send it to them. But I can't upload it to social media.

It boils down to consent. You should always always get consent before taking an action that includes somebody else. Just because you can see me is not consent to record me. If you don't have consent, don't do it. It's as simple as that.

No unless they’re doing something unethical