I've a very large legacy project with more than a million of lines of code and also with millions of quality rule violations.
The most of the violations are about "cosmetic" rules.
The point is that it's impossible to penalize the RCI for this violations, because if his priority weight is setted to 0, they aren't taken into account, but If his weigth is established to 1, the RCI is reduced to 0. A weigth of 0.1 or 0.2 would be convenient.
New applications don't have this type of problems, but people thinking in use sonar to legacy projects could have the same problem,