Try using that excuse next time sometime finds a bug in your code

I wouldn't, because that would be a basic misunderstanding the quote.

I don't understand it either. What's that quote supposed to mean? Systems can and do have unintended consequences, surely.

It's really recommended that anybody not getting it to read the article. You won't get a good TLDR.

But yeah, systems can not have unintended consequences because systems do not have intentions. It's people who have intentions, and those are not additive properties. (And, well, you can't simply add additive properties into system ones either.)

No, it still applies. What types of bug fixes and features get prioritized? Are certain features gated? Are there use cases considered too niche to support?

Nothing exists in a vacuum. The "system" isn't just the code — it's also the organization that writes and supports the software.

What properties must a system have for the quote to be applicable then?

Did you read the article? It’s about large scale systems like bureaucracies, rather then some piece of code.

My question still stands. How many people must be involved in the system design for you to consider it 'large scale'?