\[~tamas.vajk] I've left this out of the default profiles on the assumption that it will be controversial. Feel free to change that if you're confident about it.
Also, I was a little shaky on the terminology. I was tempted to use "DLL" instead of scope, but not confident enough to do it.
And finally, I didn't try to write any code samples because I think this is the kind of thing (like "Files should not be too long") that is difficult to illustrate with brevity. Jump in if you disagree. :-)
\[~ann.campbell.2] It looks good. I've added it to the SonarQube Way profile. It won't generate too much noise because of the restriction on the visibility.
A sidenote: whenever you want to write DLL, you should write assembly, because that covers DLLs and EXEs as well. But in this case the scope is better, because for an ``++internal++`` the scope will be the assembly, for a ``++private++`` one it will be the class.
@Ann, I would associate this rule to the SQALE characteristic Maintainability > Understandability and I tend to agree with @Tamas : according to the limited scope of this rule, it should not trigger some false-positives. I would even make this RSPEC targeting Java and {cpp}.