I've a genuine interest in knowing what people think is a bright enough rear light... and why? If that yanks your chain...
BSRU has at least started to express a rationale, and set a benchmark, though if his definition of bright enough is no brighter than a modern car brake light that would be "not that bright then" compared with the eyeball searing lights seemingly preferred by most cyclists.
Very few lights will surpass brake lights in terms of brightness. The key thing that makes a difference is the lens and the area of the light. Most lights aren't that powerful or that big, so what they will do is focus the beam to make it appear brighter than it actually should be. A good light with a good diffuser lens will look similar to a car brake light.
As for yanking my chain, I care not. People may not be giving you the answer you want because you haven't expanded the questions.
You'll often see people commenting that they think a light is bright because it is at arms length when they shine it in their eyes. Well of course it will be, it's arms length away. In the real world you aren't that close to the light, so in fact the light isn't as bright as many people suggest.
Going back to the original flow of comments from this article. This camera suggests that it includes a highly visible rear light, with that light being 15 lumens, that is crazily low for an LED. As I stated previously, a 10 pounds knog provides more lumens and that is a very small backup light that I wouldn't use for anything but extra lighting on things like helmets.