Wait, what? You can't host a server on your own internet connection with comcast?

Well, it's a violation of the ToS. Presumably they want to upsell you on the business plan.

Of course in practice, unless you're running a seed box or something, they're unlikely to find out/object. I've never heard of anyone getting dropped just for having a server on their home network, but I have heard of people being dropped for excessive upload.

Why not?