Has anyone noticed AAA alkaline batteries recently failing by reversing polarity? An example: 3 batteries quit at +1.1V, the 4th at -0.6V.?

It happens a lot.

Around 20 years ago, I had a brand-new Duracell C

that went backwards before I took it out of the package.

I've had other cells also do the reverse trick since then.

Expect it to happen to you several more times.

Of course. This happens if cells of different capacity are used in a series string. The cell with the weakest charge level will discharge to zero, then the remaining good cell(s) will put reverse current through it and force a reversal of polarity.