I couldn’t find one definitive answer to the question, so I thought I’d post it here :
Yes, the Asus K53SV does support 16GB RAM (2x8GB). But read on.
I own this laptop with a i7-2630QM CPU (which supports up to 16GB RAM, according to Intel), and recently replaced the RAM with two ADATA AD3S1600W8G11-B sticks. Keep in mind that each of them has a 16x512M configuration (the ADATA website gets this wrong for some reason). Lots of 8GB sticks these days have a 8x1G configuration. I obviously can’t guarantee anything, but I guess every 16x512M stick should work, of course as long as it accepts 1.5V. Your mileage may vary with 8x1G sticks.
If you have a different CPU, check its official specification on the Intel site to make sure that it supports 16GB of RAM. However, according to Asus, the weakest CPU that was used in that laptop was the Pentium Dual Core B940, and it also supports 16GB – so others should too. But it never hurts to check.
Good luck! And please post your findings if you happen to be running two 8x1G sticks in this laptop.