Is it possible to oversalt pasta water? Will the extra salt be unabsorbed or would the pasta be noticeable too salty? Is there anything people add to pasta water for seasoning (I.e ground pepper or anchovies)?
It is definitely possible to oversalt pasta water. I managed it when cooking soup noodles. I used a very small pot with to little water and then lost more water to evaporation, increasing the salinity.
This isn't to hard to avoid though. Generally one should make pasta in lots of water, and the water should taste like the ocean water. It is very difficult to salt your noodles later. According to gimmesomeoven the proper amount is
1 pound of pasta : 1 tablespoon salt : 4 quarts (16 cups) water
This sounds similar to what I have heard from others as well. This answer says the relationship between salt in the water and the uptake from the noodles is linear, more salt = saltier noodles.
One thing I add to pasta water sometimes (especially for some one pot dishes where the noodles are boiled with a lot less water, which means you can't salt as much as it will all end up in the dish) is soup boullion powder. Another recipe is drunken noodles where the pasta water contains red wine, turning the noodles red.
I think that if something is added in significant amounts and is dissolved into the water then it will flavor the pasta. Pepper is probably not dissolved into the water and I don't think it would bring much at this stage.