Comcast’s slim silver lining in its third quarter results came from the performance of its year-old MVNO business, which the operator is using to boost broadband usage and in turn leverage as a platform for selling video services. It’s one big, convoluted loop that has certainly caught the attention of rival Charter Communications. We touched on the figures in an earlier edition of Wireless Watch, but now have further analysis courtesy of our sister service, Faultline, which provides weekly insights into digital video markets and platforms. It begins with Comcast’s Xfinity Mobile service, which gained 204,000 subscribers in the third quarter to bring its mobile footprint up to 1.8m subs riding on the Verizon mobile network. But Comcast has sought…