A descrambler does not send output back to the cable company, so I don't see why it would be detectable at all.
Basically you have: ------- Cable wire
[] Descrambler
=== TV wire
{} tv
Something like this...
------[]====={}
All of the information flow is ---> that way. (At least in one-way cable areas... don't know how it works for bisynchronous cable modems)
I wouldn't worry. Just get a splitter to split the cable, send one input to the descrambler and then to the TV, and send the other directly to the cable modem. You may run into some trouble if you go through the descrambler first.