@endless I think the purpose isn't as much for rewarding as it is for a general categorisation so that people have an easier time brosing through the several dozen thousand custom wads that have been made over the past few decades. Maybe it turns out you like a certain type of maps more than others and you want to see more of that, but currently the only way to find anything similar is asking people who have played a lot of wads for recommendations, "I just played this and that, are there any similar wads?" kind of threads are pretty common on Doomworld.
