I'm not sure that this is helpful or not, or whether you're aware, but a Harry Potter fic called Rebuilding by Colubrina has more reviews than Harry Potter and the Methods of Rationality. That fic wasn't written in 2014, when the above dialogue was written, and I don't know when it overtook HPMOR, but "most reviewed" gets used somewhat frequently in this dialogue, and I've seen that metric used a number of times elsewhere,
I'm not sure that this is helpful or not, or whether you're aware, but a Harry Potter fic called Rebuilding by Colubrina has more reviews than Harry Potter and the Methods of Rationality. That fic wasn't written in 2014, when the above dialogue was written, and I don't know when it overtook HPMOR, but "most reviewed" gets used somewhat frequently in this dialogue, and I've seen that metric used a number of times elsewhere,