Heating operational amplifier OP284FSZ-REEL7
It sounds like your amplifier might be damaged. Add bypass capacitors (10 or 100nF ceramic) near each supply pin to ground though, and double check the connections before you conclude that. Make sure the unused op-amp is properly dealt with (eg. a voltage follower with input grounded). The typical &lt; 2.2mA total supply current for the two amplifiers should lead to less than 55mW of dissipation which is something like 8°C rise at the chip and 5°C rise at the case. 

What you are observing on the inverting input is a result of the type of op-amp you are using - a super-\$\beta\$ bipolar type. To protect the input transistors against reverse Vbe breakdown, they put diodes across the inputs. That's of little consequence in most op-amp circuits, however you are trying to use it as a comparator. 

Note that this particular amplifier does not have series resistance on the inputs, so if you were to short R1 or R2 even momentarily, the high current between the inputs could be enough to damage the op-amp. To prevent this you can add another resistor in series with the input signal but it would be better to use a more appropriate part.