It was implemented in some of the earlier Leopard beta's iirc. Possible speculation from my side, but it was probably removed due to licensing once Oracle expressed interest in acquiring Sun Microsystems.
This mostly died because Apple's new security framework doesn't allow for unsigned kexts or writable root. This also killed most fuse implementations and therefore kneecapped stuff like SSHFS.
Maybe Apple should consider looking into those sort of things before they promise it'll be in the OS, and even ship some barely working version of it. This was maybe around 2008 sometime so I might misremember how broken what they shipped as preview was.
Shitty shits. Literally. As for metabolic acidoses, rates are extremely low (<10 cases per 100,000 patient-years, per https://pubmed.ncbi.nlm.nih.gov/26773926/), so it's almost a non-concern.
I think this depends on the context. For your epidemiologist perspective, or looking at populations, that's a big rate! (Given how much metformin is taken) Would be easy to find people who suffer from it.
From the perspective of "Should I be worried about side effects from taking this drug / should I not take this because it might give me this effect", I think this falls under "be aware of symptoms and stop or weigh the costs if you get it, but you're probably fine".
