Yeah, just like no one would ever buy a lead-acid battery.

I don't think many people are concerned about their batteries being safe for ingestion.

That's pretty much what the article states:

> When using ferrocyanide, also consider that while this salt is relatively safe in its unaltered state, subjecting it to electrochemical abuse WILL generate free cyanide and it’s likely to pose a significant danger to you and others. For this reason, I would recommend to stay away from testing ferrocyanides in symmetric systems entirely, unless you are a trained professional and professionally well equipped to handle both the potential operational hazards and wastes generated from its decomposition products.

Somewhat true, but consumers are buying vast quantities of lithium batteries and carrying them in their pockets. Those things are eager to catch fire and emit hydrofluoric acid.

You can have safe battery chemistry or useful battery chemistry. (Not an expert, open to correction.)

Well they sell that liquid explosive terrorists use to make molotov cocktail firebombs, at every fuel station without particular volume limits at all. It's also sufficiently toxic that care is taken at salespoint to limit customer exposure to the vapours.

(these things are "all relative, if the value, measured in "convenience to the customer", is high enough, ways will be found to permit sale)

The public is not going to buy a flow battery anyway.

Or perhaps they will, but only when public is taken in the context as in public utility or public city. But individuals are not going to buy a flow battery, it is a chemical plant.

Have to abbreviate it as FCN. Cyanide is ~320 times more toxic than ferrocyanide.

There are plenty of battery customers besides the usual suspects