1. A non-transitory computer-readable medium containing instructions, the instructions comprising: one or more instructions which, when executed by one or more devices, cause the one or more devices to represent a plurality of users as first nodes; one or more instructions which, when executed by the one or more devices, cause the one or more devices to represent a plurality of comments as second nodes, the plurality of comments corresponding to comments authored by the plurality of users; one or more instructions which, when executed by the one or more devices, cause the one or more devices to form first edges from the first nodes to the second nodes based on first relationships between the first nodes and the second nodes; one or more instructions which, when executed by the one or more devices, cause the one or more devices to form second edges from the second nodes to the first nodes based on the first relationships; one or more instructions which, when executed by the one or more devices, cause the one or more devices to form third edges from first nodes to other first nodes based on relationships between the first nodes and the other first nodes; one or more instructions which, when executed by the one or more devices, cause the one or more devices to assign initial values to the first nodes and the second nodes; one or more instructions which, when executed by the one or more devices, cause the one or more devices to run iterations of a graph algorithm to obtain ranking scores, the iterations being run until values of the first nodes and the second nodes converge or until a number of iterations has been performed, where the ranking score of each of the first nodes reflects a reputation of the corresponding user, and where the ranking score of each of the second nodes reflects an indication of quality of the corresponding comment; and one or more instructions which, when executed by the one or more devices, cause the one or more devices to provide at least one of: a list of users that is ordered based on the ranking scores of the first nodes, or a ranked list of comments, the comments in the ranked list being ordered based on the ranking scores of the comments in the ranked list.