Since you basically keep saying the same thing (that it's only a destructive process, correct me if I'm wrong) I will simply address all here if you don't mind.
First let's recall AA we are talking about here is loosely the act of doing something to get rid of aliasing. MSAA for example is trying to address the issue for edge aliasing since mathematical edges practically introduce infinite frequency that cannot be displayed on any finite pixel, thus introduce aliasing.
The real AA would be getting rid of those extra frequencies on analog/continues space before sampling at the resolution of the display. Getting rid of extra frequencies generally means applying a low-pass filter. Concisely AA is applying low-pass filter before sampling (or something equivalent).
The reason blind low-pass after sampling doesn't work is basically the low-pass band your final signal can carry is already "corrupted" by aliasing.
Because how rasterisation works real AA is not practical. The second best thing is emulating the continues space with a higher resolution discrete space (aliasing of which is less then aliasing of lower resolution sampling), and do the downsampling from there. This is called SSAA also how bullshots are created. Downscaling is applying low-pass filtering and undersampling in this order (which is also what proper interpolation is equivalent to).
Since this is also expensive, MSAA tries to emulate SSAA for edges only. So What MSAA does when resolving pixels is low-pass filter (average 2 or more samples) and then only pick one (subsample).
Of course that low pass filter is a poor one, and the aliasing for higher resolution samples is generally significant but not a bad effort overall.
The moral of the story is MSAA already "blurs" before subsampling. QAA just uses a different low-pass filter, something arguably stronger (but not necessarily better). And it's not equivalent to MSAA + blur for edge pixels (since those extra samples are potentially from different surfaces).
Hence, you cannot come up with a blur filter to apply after 2xMSAA that gives the same edge quality as QAA.
when simply depend of the use of it. It's pretty notice to anyone who a minimal knowing in the matter that any AA filter 'destroy' the details in the sharpness of the picture, surely not at the level of QAA but there are a lot of variables when we compare different filter edge. The whole discussion seems try to pass the concept only in favour of a personal taste & no more from what I have readen until now, although the technical explanations are ever appreciable.
