The discussion is going the wrong way. Let me state what is the actual problem.
When the Popen() function is called with "shell=True", you cannot pass command line elements in which the characters '&' and '|' are embedded (example r'Q&A'). list2cmdline should embed such elements in double quotes '"' in the same way as when a space is detected (so r'"Q&A"').
When '&' and '|' require their special meaning, they should be passed as separate elements (r'&') and in that case list2cmdline should not double-quote them.

The whole C++ discussion was only invoked because I said a potential work-around doesn't work because the way list2cmdline is designed. That remark is not relevant, because the actual problem is different.