Will multiple chips outputing onto a bus for a few nanoseconds cause damage?
Typically the situation was avoided by the outputs being open-collector instead of tristate, with a pullup resistor to +5V completing the circuit.  If one device drove the shared line low and the other went open-collector, the shared line would stay low.  If there was only a conflict for a very short time, this would cause no problems at all.

For a practical example of this, the CAN bus is widely used in industry (particularly in cars) and operates in exactly this way.  Every device's output is open-collector with a current limit, and one device (and one only) contains the pullup resistor.  In an industrial/automotive context where devices can and do go wrong, and wires can also be shorted high or low, this ensures that no device's output can damage another device, however it goes wrong.  In addition, the CAN bus driver for each device monitors the bus to check that it goes to the expected state, and reports bus errors to the application if it finds a conflict where someone else is stomping over its data.

In practise this is unlikely to damage the chips.  However it will give instantaneous current spikes on outputs where high and low are shorted, which does unpleasant things to EMC emissions.  Designers in the 70s and 80s were much less concerned about EMC, so it's likely that many circuits went out of the door with exactly this problem.