The bad that can happen is limited by it being in LEO. If these were MEO sats but 50x fewer (Bezos sats BTW) you wouldn't be whining about it even though the potential debris would last thousands of years instead of less than ten. And appealing to the fear of the unknown is little more than motivated reasoning, the amount of rocks and rock dust entering the atmosphere dwarfs Starlink reentries.

> How sure are you that that would be made public?

Extremely sure. There are both numerous private, academic, and governmental agencies that are constantly searching for both collision paths, and collision debris.

The debris cloud alone would generate an extremely visible signature.

> Would it be always observed and caught outside of SpaceX?

Yes.

There are a great many eyes on the sky, and you can’t hide stuff up there - even every secret military satellite is known and tracked - so something as substantial as a collision would likely be known about before it even happens, as ephemera don’t change without an input.

Large operators like SpaceX and OneWeb do coordinate with each other. Ground based radar tracking data from the government is also made available to operators, and SpaceX has developed their own optical space-based detection system (Stargaze) which makes data available to other operators as well.

There's a lot of money in this stuff, lot's of planning. It's being managed by competent people who give a shit.