Can the Xfinity Set Top box be used. It appears that they block use to limit control only to their remote. The Xfinity TV app supports iPhone and connects to ALL the Xfinity apps on same network. Only volume , and mute are IR. All other buttons do not respond to IR. I have a new 4K x1 box and it requires (limits) to one dedicated physical remote.
Not aware of any issues here and certainly many, many users over time have used X1 boxes without issue. I would forget whatever you think you know from the manufacturer remote. They are of course still infrared boxes and our IR code sets have long accounted for them. For users that prefer an IP solution in an Xfinity environment, TiVo still works great.