Thanks Thomas:
The 3M liquid tape is designed specifically for this purpose. I don't believe that it would prevent repair any more than the conformal coating, but it is red in color, not clear. I'll probably wait 'til the ESC is out of warranty to do this just in case.
As long as we can easily remove it to repair any defective or failed components, it shouldn't be a problem. If you're close to the end of the warranty, it's probably not a bad idea to wait; just to be on the safe side.