ETA: We do see Elly being dim, all right. We also see her acting pointlessly upset in the furtherance of Lynn's obsessive need to vilify Rod.
Panel 1: It's night-time at the Pattermanse. We see Elly with her trademark scowl trying to put as much distance between her and John as she can without falling out of bed.
Panel 2: As he reaches over to touch her, she says not to touch her.
Panel 3: She, you see, is angry and wants to be left alone. Why she's angry is anyone's guess. Perhaps John said that it doesn't actually matter in which order flatware is dried just so long as it's clean. Maybe he made a compliment that she was too dense to understand. He could have even implied that she was directly responsible for the evils that she whines about.
Panel 4: In any event, John tells her if that's what she wants to do, that's fine with him.
Panel 5: As he seems to fall asleep, she scowls a bit more.
Panel 6: A few minutes later, she does what she always does in any sort of confrontation: she backs down. This is made manifest by her scowl turning into a panicked frown.
Panel 7: She reaches over to John in an effort to make things right.
Panel 8: He makes the mistake of pointing out that he knew that if waited long enough, she'd come around.
Panel 9: He then asks what he did this time when she goes back to being pointlessly upset. What he did wrong, of course, is marry an amazingly thin-skinned woman with very little brain who hates being called on her bullcrap.
Summary: Lynn should have called this strip "John can never, ever win an argument with Elly." That, or "Elly is always right."