TMUX136: Input voltage range for COM1/2

Hello!
The VIH is referenced to the SEL and /EN pins since those are digital logic pins. The COM1/2 pins do not control any logic but rather are passive and only allow the signal from A1/2 and B1/2 to pass through the switch therefore there is no VIH level for them. 
The maximum voltage that is recommended to pass through these channels is listed in the Recommended Operating Conditions under "V(I/O)". This voltage would be from 0 to 3.6V independent of what the supply voltage is. However, the SEL and /EN voltages should never exceed the VCC supply voltage. 

Thanks,
Rami 

There is no VIH for COM, therefore there is no limit (however there is a maximum recommended voltage as I stated above). COM is the common connection for the switch, where either A or B ports will short to. The voltage level at the I/O pins will have no impact on the logic levels. They will simply create a connection for the passive switch to pass the I/O signal through. Depending on the logic implemented on the SEL and /EN pins, the COMx will either short to Ax or Bx or switch to a high impedance state : 



COM1 would only output to A1 in the case of your circuit. It won't drive both signals to both A1 and A2. COM2 would be connected to A2 when both /EN and SEL are low. Currently you're COM2 -> A2 connection is floating on the COM2 side. 
The VIH and VIL levels are for the SEL and /EN as these are the digital logic pins that will determine how the switch will react. 

The VIH level for both the SEL and /EN pins is 1.3V and the VIL for these pins is 0.6V. 

Thanks,
Rami

You may leave unused pins floating but it is recommended in high speed applications to terminate them to ground through a 50ohm resistor.

See TI Precision Labs - Switches and muxes: Can I leave unused pins floating?

Thanks,
Rami