Good catch Mac
I just rewatched that segment(10 min into the show and paused it exactly where your screen shot was taken) and saw as you did. Titles for the most part stayed clear but the background really looked bad
I agree that somehow the distortion must have been present before the titles were added
When I see macroblocking on bitstarved SD channels the titles are always the first things to get fuzzy, this is odd.
I posted a similar question in my local OTA forum but no one has responded. Either they aren't noticing it or aren't watching these shows.