"Just taken a pair of dead Duracell AA cells out of a TV remote that had been laying around a long time - no evidence of leakage at all. "

That does not respond to what you responding to. He is talking about counterfeit batteries. What's more, heavy duty cells should not be used in remote controls because their power drain is so low. Operational battery life approaches shelf life.

"One had a bit of corrosion on the negative contact, the other was clean. "

Also proves nothing. A Kodak is a different brand and even if they were made at the same factory it could have been to different specs. And corrosion does not prove a leak at all.

If people are really getting leaks in those Duracells it is actually more likely that they "streamlined" their manufacturing process.

To know for sure you need to cut the thing apart and measure everything and then do a chemical analysis. If that fails to prove anything then you have to cut some more and look at the seams for defects. For a AA battery ?