> This will load all comments with a single query. This reduces the total number of queries to 3. More generally the number of queries will be 1 plus the number of associations named (except if some of the associations are polymorphic belongs_to - see below).

Good call. Still, the difference between 1 and 3 queries is nothing compared to 3 and 100s (n+1 problem).

I wonder what AR can't turn that into a single query.