We run a website where we send transactional e-mails using Amazon Simple Email Service (AWS SES). Once in a while we get back a delivery status report with a complaint. (Strangely, a lot of these complaints are about order confirmations.) These, of course, do count against our account reputation, and I was always wondering where does this nuclear complaint option sit.
So I looked into a lot of these complaints, and all of the recipients are Microsoft addresses, so hotmail, live, outlook or msn. Apparently this is the Report Junk / Report Phishing option.
So if you use Hotmail / Outlook for web, and you receive unwanted review prompts from the stores you bought from or all kinds of Trustpilots that somehow got your personal data, reporting Junk and having it issue a complaint is the least you can do.
If you have it connected to an e-mail client, like Apple Mail, Mac Mail, Office Outlook etc., in my opinion you should still use the browser interface, because the client is likely to merely move the email to the Junk folder, which will help the spam filter learn and that's it.
Lastly, of course this is unlikely to work with plain in-your-face spam, as they use disposable emails/servers and they don't care about the sender reputation.