What a thoughtful comment! I concur that the chance of mirror-life 'evolving naturally' (or "in the wild" let's say) is basically zero, but then I imagined a future cell-printing machine that 'wild' humans might make that prints (maybe at near the atomic level), and that made me wonder whether given such a printer you could just swap to opposite-chirality (mirror) ingredients, and maybe mirror the 3d plan that you're printing? Doesn't seem that far fetched if we ever get printing at a very small scale level? But then I remembered a cell is more like a wave than a static object, so all of the above are probably meaningless ramblings.. but all in the spirit of curiosity!

I am not alarmed by the possibility of mirror life because I think it would be at a disadvantage to all other life on earth at present, so it probably wouldn't get very far. (famous last words!?)

That would definitely be possible but if humans had the kind of molecular nanotechnology that could do that I'd be much more confident in our ability to whip up some phages to counter the threat.