I am not sure what you have under your car, but had you read the entire link you would have found that the later E46's have a "jack pad" installed on that center jacking point (the one marked in red in the photos) and that is where they jack the front of the car from. The older E46's have that spot that has been crushed, however it is the jacking point, according to one post; "It is ok to crush the middle jack point, or the one circled in red if you have been following this thread. In the latest copy of Bimmer, issue No.66, you can read the article by Guru Mike Miller on winterizing your BMW. He goes into detail about lifting that will answer all of your questions on this thread. Mike said that he said that you can crush this jack point so I did. No problem looks bad but that is it. Hope this helps any speculation."
I also noticed someone posted that under that crushed part is the hole that BMW later installed the jack pad in. As far as the rear of the car goes, use the diff brace, not the diff and that should be fine.