You need to make your camera track the on-screen render position, not the logical position before rendering.
Ooh. That makes a lot of sense. I did what you said and it fixed the jittering during constant movement, but there's still jittering while the camera builds up to the player's speed.
I ran the game at 10% speed and output the camera's delta and position, holding a key to mark the jittering frames when I saw them.
It's not super accurate because of my timing, but it seems like it only jitters when the camera moving more than one pixel per frame. The player moves at a constant speed of 1.5. When the camera is at 1.5 delta, it alternates between one pixel per frame and 2. Not sure how helpful this information is.
I could possibly clamp the camera speed below 1, but that's probably too slow, and just a workaround rather than a fix.