I think even a Japanese person explained that grabbing one's head out of frustration is a common thing to do, especially for Japanese culture. So I don't really get the point about Levi "getting a headache"?
I don’t think it’s a headache, but I understand people zooming in it. It’s the first time Levi has done this, and it happens in a chapter that specifically mentions headaches as an Ackerman trait.
Personally I believe this panel is a red herring. It’s designed to make us wonder, however briefly, if Eren’s Ackertalk is accurate. I don’t think it is. Not Eren’s speech nor the headache. There’s no sfx to indicate headache and it is just as easily explained as being situational. We’ve never seen evidence of Levi having headaches despite frequent disagreements with Erwin. Or Kenny for that matter.
I also puzzle over the idea that the head grab could indicate a change of liege, especially when Levi’s promise to Erwin is given special focus as he is literally kneeling before him in knight/liege fashion.
So yes, I agree with you. I understand the talk surrounding the panel, but not many of the possible interpretations.
Thanks for the ask!