A big meteor could punch through both the concrete dome and the underlying steel containment. If that happens, we will probably be glad it hit the reactor and not nearby New York City. As long the meteor doesn't replace the steel containment structure with a crater but merely damages it (after obliterating the dome), we have at worst a second Fukushima. What made Chernobyl so bad was that the cooling water caused a giant steam explosion, carrying radioactive material high into the atmosphere. That failure mode is impossible in any reactor operated today.
If we were to assume that falling satellites hit nuclear reactors with a frequency of once every 200 million years, how much money do you think should be spent preventing accidents of that type?
Additionally, the chance of orbital debris striking any particular location on Earth is nearly zero, so it's a bit foolish to over prepare for something that is less likely than winning the lottery several times in a row.
1. absurdly low probability
2. power plants are built to withstand airliner crashes having far more energy
3. it'll be insignificant debris, broken smaller than pieces of that space shuttle
4. the comment smells like nuclear fearmongering
It may be wrongly assumed that everybody here is nerdy enough to know all these things.
As for 1., sure, but still (probability x damage) makes it nevertheless reasonable to consider it, even if it is later dismissed.
4. - agree, and that's my problem. Sounds like [1].
However, the chances of hitting it by accident are absurdly tiny. It would be pretty hard to hit from orbit deliberately; maybe the only people who could do that are SpaceX.