During the comet strike, the Hyatt Regency Hotel (with its distinctive Compass Room revolving restaurant on the roof) can be seen crumbling from the shock wave. As the credits begin, the smoldering cityscape is shown (something about the Phoenix will rise from the ashes)...with the hotel virtually unscathed.
In the scenes from the control room for the rocket that will carry the nuclear warheads to the comet, a computer screen is shown with a graphic of what is presumably the rocket. Actually, the graphic on the screen is a distillation column connected to two kettle reboilers, commonly seen in control rooms for chemical processing plants.
Despite two nuclear explosions in the region of the comet's tail, it is explained that the comet and its trajectory were unaffected. Since space is a vacuum the blast wave from any nuclear explosion or explosions so close to a comet (or similar object) would affect its trajectory in some way.
There are frequent shots of the comet as seen from space showing the comet quickly brightening and darkening. From space the comet's appearance would remain virtually unchanged except for increasing brightness as it nears the Sun. In variation in brightness would be visible from Earth due to atmospheric disturbance, not from space. The comet would only brighten significantly as it impacts the Earth's atmosphere, moments before it explodes.