I had a low-stress application for reusing alkaline cells (low current, didn't necessarily need a full recharge), so I tried it myself [original research] although [this ain't Wikipedia]. The first thing I discovered was that the available information is so dead-set against trying this, that it is very difficult to determine what the proper terminating voltage would be. I used a bench supply so I could limit both the current and the voltage.
On the first try, the results were good. On the second try, the cell leaked. After that, I intentionally kept the charge current to C/10 or less, using cells that had never been recharged, and that were not completely exhausted. After some period of time, the cells began expelling gas and electrolyte. The gas leaking was audible (as in, "What's that sound?", and "Oh, it's the cell I'm recharging")
As an aside, cells that are intended to be recharged often have mechanisms targeted at absorbing the gas, or at least safely venting it. Not in this case.
Conclusion: The chemical reaction isn't necessarily "reversible" in an exact sense. When run backwards you get other things like heat and gases. Electrolytic reactions involve things like dissolving metal, and the resulting corrosion products don't automatically know where to go back to. In the end, I quit trying to recharge these. No deaths were reported.
I believe these results will vary with brand (manufacturer), so if it worked for you, you were just more lucky. But this is an example of why it may not work.