Sean,
you may not produce a ranking list explicitly, but if we take all your reviews and sort them by your numbers, then there is your ranking. So you are doing all the legwork. If you were to just write textual and pictorial reviews and not assign any number, then I would buy your argument, because you would explicitly make it very hard for the reader to compare courses.
Numbers are for relative comparisons, but by themselves they are not mathematics. They are just stand-ins for lists like "great", "good", "mediocre", "bad". If you wonder in your head whether you should spend your vacation in area A with one great course and two mediocre ones or rather in area B with three good courses, then the mathematics start. But you (the reader of the ranking list) are doing the mathematics and you are, for example, subconsciously assigning a 7 to the great course, 5s to the good ones and 3s to the mediocre ones. Then you add it all up and arrive at a conclusion - that's your mathematics, whether you do them algebraically or symbolically.
And perhaps we can agree that doing these mathematics are not the business of the rater, because he cannot know the individual's weightings.
cheers,
Ulrich