I have added about 4.8 qts of oil to my WRX and drove for 3-4k miles so far. When I checked the fluid level this morning, it was indicating that it has more than it should. What would be the consequence of having let's say 1 extra quart in the engine? should I drain the oil until it is within the allowable level?

If you drained out all the oil and then added 4.8 quarts with a new filter it isn't overfilled. The dipstick can be tricky to read properly, make sure the car is on a level surface and has been sitting for a while, pull the stick out, wipe it clean, reinsert fully then take it out and read.

I find that polishing the XXXXXXX area on the dipstick including the small open holes and the notch with some 600 grit until it is shiny will allow a much better visual on the oil level and actually lets the oil stick to the stick.

It's only overfilled if over the notch above the top hole when the oil is hot. ed

I change my oil and filter and just dump the whole 5qt M1 jug in and done.....the extra 6.4oz. isn't gonna hurt anything....

If you drained out all the oil and then added 4.8 quarts with a new filter it isn't overfilled. The dipstick can be tricky to read properly, make sure the car is on a level surface and has been sitting for a while, pull the stick out, wipe it clean, reinsert fully then take it out and read.

The reason you wanna let the car sit for a while is to allow residual oil to drainback and to let it cool...when it gets hot it expands which could give you a reading of having more oil than you actually do. As far as actually having too much...I have heared it is not good. Not sure why or how much will actually matter. The manual talks about all of this though.

Assuming that you actually have too much oil in the engine, yes, you should drain it. Having extra oil is hard on your seals, and it also tends to foam up, which makes it lubricate poorly. You might also get unburnt oil in the exhaust, which isn't good for your cat.

I think that shemoves is correct, in that I seem to remember the manual having a paragraph or two about what happens when you put too much oil in.

From personal experience, overfilling with oil can often lead to leaks around the valve cover gasket. I don't know if that's the likely place in the boxer engine design, but I think you'd see leaking around a seal somewhere. If it's severely overfilled, the rear main can go(had that happen on a S-10...no fun getting the oil place to cover that one).

Yes over filling is very bad for your seals. Causes many leaks.