Aha! 05:37 Mar 8, 2015
Well, I can see for a start there one of the things that must be confusing you, and does help the whole thing to start to fall into place.
"elle porte suré does not mean 'it brings on' — the construction 'porter sur' has a quite specific meaning, which may sometimes (but not really here) be likened to the notion of 'it covers' or 'applies to', for example.
Also, 'si' in this sort of construction is often best considered (if not actually rendered) as 'even though' — you can immediately see the meaning of your sentence suddenly beginning to fall into place. | 
peer agreement (net): +1
