I don't see any big objection to connecting the 3.3 V pin to AREF, providing you take precautions in your code.
The default for AREF is so-called DEFAULT (heh) as here:
uint8_t analog_reference = DEFAULT;
Once you do an
analogRead the analogRead code connects up the desired analog reference:
ADMUX = (analog_reference << 6) | (pin & 0x07);
Then it starts the ADC conversion.
If you change the analog reference voltage then this needs to be done before doing the analogRead. eg.
analogRead (A0); // use external reference
The reason they do it this way is so that it is safe to physically connect up the 3.3V pin to the AREF pin, because the initial state of the processor is to read the AREF pin.
Once you do your first analogRead, and with the DEFAULT reference voltage used, you will find 5V at the AREF pin. If you had then connected that to something else like the 3.3V pin, it will short out and damage the board.
void setup ()
pinMode (13, OUTPUT);
digitalWrite (13, HIGH);
int foo = analogRead (0);
} // end of setup
void loop ()
} // end of loop
Put your meter on AREF and you will see it jump to 5V after 5 seconds.