True that q080 or even 720 is not uhd, however alot of TV's (mine are Hisense, Vigio, and Mitsubishi)
All hd and one is UHD 4k. They all have upscaling. This means they will make a point turn better quality even if it's not HD. What I believe the question above was he was asking does the x1 box make hd look better (i.e. upscaling) even if it's not 4k?. I am not a Comcast rep, however I am hugely tech savvy. I'm the guy friends and family call before tech for things.
So here's my best guess by experience, if your TV has upscaling (ask Google if your TV model does to find out) and you do have an x1 box, it should look better if your TV is seeing uhd compadibco box. When I turn on ps4 pro 4k is shows my inpits now as uhd HDMI instead of just saying HDMI with Comcast box. You also need to go into TV settings and change HDMI from standard to enhanced to Allow for rgb uhd. You may need a better HDMI cable f yours isn't a good one. The old HDMI were designed for 1080p and 4k MAY suffer some quality if yours isn't compatible.
Hope this helps some, if not I will try to answer any questions regarding settings of your TV and HDMI cables. Please ask techs for Xfinity related tech questions.
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