These kinds of discussions are pretty sad. The genre could be so much better and broader if people had a more nuanced view of what rogue is, how its successors expanded on rogue, and how new games might expand on what's been done before. Roguelike should mean "in the tradition that started with rogue," not "replicating the mechanics (but bizarrely, not the theme) of rogue." Of course, this is just another discussion of why the so-called "Berlin interpretation" sucks (lol, btw -- the great minds behind the rgrd web-based diaspora got together to set down the fundamental intellectual framework of roguelike development, in much the way physicists of the early 20th century codified the principles of quantum mechanics in the "Copenhagen interpretation").
Roguelikes have to be turn based (according to a nonsensical definition of "turn based" -- i.e. it just has to wait for user input before anything happens). Roguelikes have to be single player. Roguelikes have to regenerate the world when the player dies.
So in other words, all the interesting avenues that people have considered any time they've talked about their roguelike experiences with someone other than the walls of their dorm room can never be realized within the genre. What if my guy met your guy in a dark alley? Well, that's not possible and if it happened, the game wouldn't be a legitimate roguelike anymore. What if I want to play co-op style with a buddy of mine like we do in D&D? Well, even if there were a game that let you do that with terminal graphics, a grid based map and interface, keyboard commands, random maps, items, and monster behavior, that wouldn't a real roguelike, especially if it allowed you to bring dead characters back to life like you can -- in principle -- in D&D.
The distinctive idiom of roguelike games is not permadeath, it's random and/or procedural generation of game content (and, not coincidentally, this is the mechanic people appropriate in commercial games marketed as "roguelike"). Unfortunately, too many people have allowed the interaction between these two notions in the context of a single player game to confuse the issue. The result is a stagnating genre, increasingly being overtaken by marketing efforts from companies making games with little to do with roguelikes. That's great for people who want drive web traffic, not great for people who want to see advances in line with what's been in the nethack FAQ for over twenty years.
(Also, I'd like to distance myself from this nonsense about permadeath not making games more difficult -- this is so obviously and straightforwardly wrong it's amazing there could be controversy. I'm all for permadeath in single player roguelike games, I just think the emphasis on permadeath is wildly misplaced.)