And literally everyone (including us gun plumbers) removes them from C7s and C8s (at least in Valcartier).
If you guys are talking about CF C8s, we never had C8A2s. They were never bought and were never in the system - ever. They are different rifles with different barrels. We've had the C8FTHBs (with the black furniture and no ambidextrous controls) and C8A3s (with the green furniture and the ambidextrous controls of the C7A2).
And yup the top rails on the receivers of the CF rifles sit higher than regular AR-15 top rails. I think this is also true for H&K 416s. This is why A.R.M.S. makes a flip-up rear sight especially for C7s and C8s. If you bought a commercial flip-up rear sight you'd find out that they sit higher than the front sight. From what I saw, judging by pictures only, the rails on the civilian models are the standard AR-15 height and should be fine.