Level 3 is the backbone provider. They are one of the people who handle the internet traffic once it gets out of your neighborhood to the rest of the world. But dont forget that cable is a shared connection to you and your neighbors. So it might not be that a family member is eating up bandwidth, it might be other places. That said it does seem endemic to Comcast as a whole if they are either doing DPI (deep packet inspection) and prioritizing bandwidth or there is an issue further up the line where it is in common to more people.

However, this board is pretty small in terms of the traffic it delivers. There are some graphics (pretty small) and lots of text (very small) so it should load very fast (as it does most of the time).