I bought my car with what looks like dealer installed moldings on the doors. If I were to remove them, would there be "tan lines" and can they be buffed out?

 

If your car is an 04, then yes most likely. Whether or not they buff out depends on how well the paint has weathered the last decade. But similar to debadging, there will probably be "ghosting" and some if not all of it can be resolved with a good polish and buff. Worst case you can always just put the molding back on if you're not happy.