LM1496 maximum input voltage
Although the abs max for the supply is given as 30v, which is determined by collector-base and collector-emitter junctions, the abs max for the differential inputs is only 5v. 

If you look at the schematic for any of the differential inputs, you see a pair of common emitter transistors, with the input applied across their bases. Any base-emitter junction when forward biassed looks like an ordinary diode, and will start conducting significantly at 0.7v (ish). However, the reverse biased emitter-base junction is not a 'good' diode, in most silicon BJT implementations that junction breaks down at around 5v, and not particularly robustly like a zener diode diode does. Significant reverse breakdown current can damage the transistor. The purpose of the diff input limit is to keep those junctions out of reverse breakdown.