If you are satisfied with the results, great.
But there is loss of quality which is why mp3 and aac are called lossy formats.
If I take a cup of water and freeze it, then thaw it out again, is it something other than water?
It's not the same. You are freezing all the water.
Converting to a lossy format does not retain all the data. The file size is reduced by throwing away data.
When you burn it to an audio CD, the original bits are not magically returned.
Burning a purchased download to a CD converts the data file from a 128kbps mp3 to a 44100kbps aiff file which is exactly how it would be if I purchased the CD retail
It may have the same amount of info but it is not even close to the same info.
Ripping it back onto the HD simply reverses the process
Sort of. It puts all the info from the mp3 back onto the CD but you have already thrown away when you converted to mp3 the first time.
All it takes away is waht was "put back in" when it was burned.
No it doesn't because there is nothing to tell the RIPper what was put back in.
RIP an audio CD to mp3 or AAC at 32 kbps and see if you can hear the difference between the CD and the RIP'd file.
Then burn that file back to an audio CD. According to your post, it will now sound exactly like the original CD.
Every time a file is converted from anything to a lossy format, data is thrown away.