[bryanlarsen]

Eccentric orbits mean higher apogee but also lower perigee, which for something at Starlink altitude likely means perigee is below the Karman line. Which means they'd deorbit within 90 minutes. So they'd only have one chance to hit something in higher orbit. You won't get enough collisions to start Kessler.

[mattashii]

Starlink operational orbits are generally >500KM high (original license "at 525, 530, and 535 km", -Wikipedia).

I think it is not unreasonable to expect any debris clouds from Starlink to impact orbits from 300km to 700km for many months, if not years. Even if the debris with highest eccentricity will quickly burn up in the upper atmosphere, there will likely remain a significant portion in orbits that are eccentric enough to be problematic for higher orbits for years, (slowly?) cascading the debris orbits upward. It doesn't have to happen immediately after impact, but kessler syndrome doesn't have to imply 100% guaranteed loss in a day either.

[bryanlarsen]

Debris has a much higher surface to mass ratio than satellites due to their smaller size and irregular shape. Therefore debris deorbits much quicker than satellites do.

300km orbit decays in about a month, so the risk is already reduced significantly.

And there's not much in the 500 - 700km range now. Kuiper will be there soon, but anybody that takes out Starlink is also going to take out Kuiper.