R1 should be able to supply 5 mA for a LED without disturbing the circuit. If ronv concurs, might connect U1 output to the base of an emitter follower like a 2N3904, collector to +12V, & emitter to 2k, other end to LED anode, cathode to ground.

But this won't differentiate between the "pwm state" and the "steady on" state...?

EDIT: If I have an indicator, I can spend some time working with this basic circuit, tuning it for different motors, voltages, loads, etc. Although comparitors & opamps might seem simple to many of you folks, I have very little experience in this area, and so this project seems like a good start for me to familiarize myself with their operation.

 

R1 should be able to supply 5 mA for a LED without disturbing the circuit. If ronv concurs, might connect U1 output to the base of an emitter follower like a 2N3904, collector to +12V, & emitter to 2k, other end to LED anode, cathode to ground.

Sounds good to me!
Edit:The brightness may vary. Hard to tell how much.

 

You could cap. couple a high impedance speaker to emitter , in parallel with R & LED. You can hear a wider range of buzz than the LED can show ??