I started a thread on this a few months ago, and I absolutely agree that bright strobes are hazardous on a path. The whole point of strobing lights on a street is to make you more noticeable in the driver's peripheral vision, not to make it easier to locate you from straight on.I have seen some of these strobes on MUPs from at least a half mile away in broad daylight, and then found myself completely dazzled when they close the distance to the point I couldn't actually tell you where they were on the path. Even more significantly, they obscure other oncoming traffic from my perspective as it is absolutely impossible for the human eye to adjust to a bright strobe--your pupils cannot react fast enough.
The worst case of this I've seen was a man riding with one of those strobes on a shady path, and I really could not see anything around him but his light. As we closed, I realized to my horror that there was a small child riding with him on his own bike, and I didn't even see the kid until I was within about 15 feet. Normally, I would have yelled at the guy to turn off the strobe, but I needed to concentrate on making sure the kid didn't swerve into my lane (as kids that age often do). My practice on paths is to always slow wayyyyy down when I see an oncoming small child even if the kid is way over on the other side of the path, but I had not done so in this instance because I had no idea the kid was there.
I've never found bright lights during daylight to cause me problems unless they're strobing. Even a slow blink rate isn't a problem, but strobing is very disorienting--it's used for that deliberately in tactical situations. Pointing it at someone who is going to be passing within a few feet of you is a very, very bad idea.
Side note--two or more asynchronized strobe lights makes the disorientation even worse. I've noticed a lot of these are on both bikes of over-equipped couples. Also, if I can see it from a half mile, it's going to be absurdly bright when we close (point of maximum danger). Google the inverse square law if you don't understand why.
Please call people out whenever you encounter this--the most common reaction I hear is "I had no idea, no one's ever complained."