Yes, you can make a complaint about a WordPress.com blog. Ok, look very carefully at my wording. I said WordPress.COM blog not WordPress.ORG.
A WordPress.com blog is hosted by WordPress. Whereas, the WordPress.org is self-hosted. That means you purchase the hosting space for it to live. Which means if you are on a hosted site with WordPress.com you site can COME DOWN when they find that it is against the terms and agreements. YOU HAVE NO CONTROL.
Now, it is important if you are using a WordPress.COM site that you know the kinds of things that qualify as a compliant. It is also important if you see a WordPress.com site that you may have issues with.For example, I have found some of my articles posted on splogs. Those are fake blogs, usually reusing content from other sources, used to generate link spam Many have incorporated my articles into spam material. Most of the time the site does not make sense. It may also be high on the porn end.
WordPress.com is an excellent platform and I start almost everyone I coach with a WordPress.com site to get used to basic blogging. But never encourage them to stay there if they are promoting a business. Instead, I encourage them to transfer to self-hosted WordPress.org so they have more search engine juice and steriod like functionalities via plugins etc.
So, you can view the policy on complaints from WordPress.com. It is an eye-opener.