My 1999 Impreza also has had problems with paint: too thin, peels after four years (bought the car new) and scratches easily. Too bad Fuji Heavy Industries can't spend a little more on their vehicle exteriors - and, say, use Rustoleum or a heavy, durable paint!
Unfortunately this is how all new cars' paints are now.
The best suggestion I can give is to use a sealant first, and then wax over the sealant.
I'd suggest using Klasse's sealant.
I don't know where you live, but here are Canadian and American sites you can buy it from:
I used it on my 2010 Impreza WRX, and it works GREAT!
There's a lot missing on this review. How do you wash your car? I stay out of automatic machine car washes, and wash by hand. I have seen people wash cars with dish detergent, stripping off the wax. Then they use the wrong towels vs microfibers, and scratch the paint and clear coat. You need to use automotive car wash and high quality wax. I have the car completely wetted in the shade and rinse my wash towels many times. Black is a color you have to be even more careful with.
I live in United States. I buy where the auto detailers buy online. My favorite products are US Auto Supply in Philadelphia. I also like the spray bottles of gloss enhancers. I stay away from silicones inside the car. A lot of retail automotive stores have products I shy away from. I do a lot of car shows, and found good people to ask are the ones winning the trophies.
Lastly, it's amazing what a clay bar can do. It's as much technique vs the paint. Do it wrong even one time and it can a very costly day for you.
Washing by hand definitely helps. Staying away from highly compressed water pumps is also important.
I am the one with a 13 Outback, and surely the paint layer is very, very thin on them.