Dead code is a code smell. Dead code is code that has remained around but is never reached or called. It is very common to have dead code in older projects that have not been cleaned up. While being a very common code smell it is also very easy to fix.
Code comments are a code smell. This statement might feel contrary to reason when you have been taught to always comment your code. Having comments might however tell you that the implementation is too complex.
Don’t get me wrong, I am not saying that you should not write any comments. You should however pay attention to when and why you are writing them.