The other answers have focused on why the bug you've put in hasn't been addressed, but I'm going to focus on the part of your question where you ask "What should I do?" The answer there is that if you feel very strongly about the bugs, you should learn the skills necessary to fix find them, and fix them. In this way, OSM is like any other FLOSS project. The best way to get something you want done within the project is to do the work yourself. In this case, it might mean to learn Mpnik, Mapnik, and learn the rendering rules you want, then submit them back. You may find they get approved. If not, you can run your own instance where the rendering is exactly how you want it.

The other answers have focused on why the bug you've put in hasn't been addressed, but I'm going to focus on the part of your question where you ask "What should I do?" The answer there is that if you feel very strongly about the bugs, you should learn the skills necessary to fix them, and fix them. In this way, OSM is like any other FLOSS project. The best way to get something you want done within the project is to do the work yourself. In this case, it might mean to learn Mpnik, and learn the rendering rules you want, then submit them back. You may find they get approved. If not, you can run your own instance where the rendering is exactly how you want it.