Won't it also kill you if you put something acidic in the bottle? Like water with a spritz of lemon? That's why copper pots have a lining, anyway.
https://en.m.wikipedia.org/wiki/Verdigris
Yup, and although correct about coppers antimicrobial effect it only kills bacteria on contact. So I suspect a majority of any bacterial contamination in the water, will never come in close enough contact with the copper walls for it to have any real effect.
Water bottles, if not cleaned properly with a soap and brush on the inside, will be coated with a bacterial "lawn". Copper prevents that. Lots of bacteria need such a lawn to propagate, only some can multiply without a substrate. So even if the "free" water part won't be desinfected, copper has an overall positive effect on the bacterial content of your drinking water.
As someone who washes my (steel) water bottle at most 1x a week, and drinks ~10-14L of water a week, I've never gotten sick from drinking out of my bottle before.
You can usually tell if the water in your bottle is going bad / filled w bacteria..
No. I was just explaining why copper is better in that regard, not that I would personally care that much. I do prefer stainless steel, because it is more robust, dishwasher-safe and cheaper.