Note 142 — VII Language as a Historical Product: Drift
Reading edition
Footnote 142: Aside from the interrogative: am I? is he? Emphasis counts for something. There is a strong tendency for the old “objective” forms to bear a stronger stress than the “subjective” forms. This is why the stress in locutions like He didn’t go, did he? and isn’t he? is thrown back on the verb; it is not a matter of logical emphasis.