I had a similar problem to yours with some commercials looking choppy. I have a Sony A8G and a cable box on one of my HDMI inputs. In my TV there are two settings for dejudder (included under the medium and high settings of "Cinemotion"). When I first got my TV and hadn't used things much I'd decided on medium because it seemed to give the best performance for when I was watching shows - I thought it locked onto video for dejuddering slightly better than the high setting (I could have been wrong though, it was close and I wasn't exactly a/b ing cable shows)
Your problem could be that the commercials are doubly juddered (juddered at the source and juddered going from cable box to TV), and so, some frames are displayed for longer than the time in milliseconds of normal, single judder of 24fps on 60hz.
Your TV just might not have the software required to compensate for it. I assume your TV's dejudder works like my TV's medium dejudder setting - on frame timing. It likely looks for the first and second time a frame is held for more or less time, and syncs itself for proper pulldown. If there's judder on top of that, you're SOL.
I think the high setting actively looks for frame changes, stores 2-3 frames in a buffer to be sampled and held at a steady pace. Slightly more work and probably with it's own problems causing, on average, more dropped frames than the standard way - so why it's a secondary option
If it's just commercials, I wouldn't worry about it. I only noticed needing to go from Medium to High on my TV's dejudder setting to fix commercials. Motion handling is one of the reasons to buy a Sony TV over other brands, they do it best. I wouldn't return the LG over it, but if it's affecting TV shows, you might have to.
edit: As far as I know, this isn't something reviewers look at. I haven't seen it mentioned anywhere.