When Americans complain about Comcast, it's not a meme, they are actually an awful company.

But for the record:

If you just sign up for Comcast (XFinity, whatever) and use the internet, you are renting a modem/router combo from them for about $10 a month, in perpetuity. You can buy an off the shelf modem/router for a couple hundred bucks, and use that instead. It'll pay off in a year or two. You have to call Comcast up and activate the device, but it's otherwise a completely painless process.

Yes, they do.

Further, my experience with Comcast specifically is that every three months, they "forget" that I don't rent a modem from them and just start charging me the rental fee anyway. Then I have to call them up to tell them to remove the charges and stop adding new ones.