When subtracting 15 from a powered subtracting comparator, and then turning off the input, the input lights (the 2 on the back) dont turn off.
Turning of the side input doesnt affect it either.
Only if you remove the hold on the comparator, and then turn it on/off, the lights will switch off.
Here's a pic:
https://www.dropbox.com/s/yjswhu66nj6faox/2013-02-12_21.56.57.png
(its really hard to upload files for me on here)