They were likely told to stop participating in discussions around the letter and then they didn’t. The verge article mentioned there were huge internal discussion threads.

I am surprised that rejection of an order could be grounds for instant dismissal in the UK. In Germany that would involve a lengthy process of legal letters to an employee. Something like 3 strikes. Also you can't just order anything from an employee. It's not the military, right?

The work culture in Germany is also quite different I imagine. My impression is Germans take their work very seriously. There is simply no room for the crybaby BS that has become all too commonplace in the American workplace where people have deluded themselves into thinking they are there for activism first and work second.

This indeed - the professionalism displayed by my German colleagues is incomparable to that of my erstwhile American colleagues. Much higher maturity levels even for people of the same age group. Not surprising that worker councils are also treated seriously by higher management.

You're right; I looked it up.

The direct order has to be something important that is part of your job.

Less-serious insubordination should be dealt with by means of formal warnings, and processes to help the employee improve. But if, for example, I'm ordered to attend a customer meeting at 10:00am, and I refuse on the grounds that I'm planning to stay in bed until 11:00am, I can be fired summmarily. The employer would be well-advised to document everything scrupulously.

Ultimately an employer can fire anyone they want; HR processes and procedures can be rigged. In a legal dispute between an employer and a worker, the employer has the upper hand. If a worker wins an employment dispute, they might keep their job; but they now have a hostile employer.

Insubordination is more than refusal to obey a direct order, at least in America. See, for instance, the uniform code of military justice article 91.

Thanks. My remarks were about normal employment; insubordination in the military is probably quite a different matter.