Two notes here:
Firstly, I think the argument that showing numerical data takes away from the realism of mud combat is idealistic at best. Let's be real here, the old cliche that a mud is a storybook is true only when it comes to creatively written room descs, quests and so on. Mud combat does not, and probably never will, read like a book. If I opened up a fantasy novel and the fight scenes were: "You brutally slash the orc! You bash the orc, sending him to the ground. You lightly scratch the orc. The orc misses you," I would not stick with it long. Mud combat is a numbers game, just as combat in any game is, and trying to promote it's realism through pretty text just isn't likely. There are a very, very few muds that do it, and those tend to be manual combat muds that were specifically built around that same combat system. If you have any vestiges of the original "kill mob" code in your mud, trust me, realism isn't part of the discussion.
Secondly, specifically to those manual combat muds, or pk heavy muds in general, you'll find that this is where numbers pretty much have to be shown. I can't imagine godwars2, or the old Konquest mud, or assault or any other number of pure pk muds functioning without numbers. That is because you need the data in order to respond effectively and quickly, and due to the fact that players are not going to give you the luxury of experimenting. And even if they do, experimenting should be fficient and to the point. It's much simpler to test out a sword and realize it isn't doing damage, so you go rebuild, than it is to test out a sword and ponder the ambiguous language chosen by the mud's dev.
So, where pk and competition counts, numbers will be crucial. If you don't care much about combat, or try to minimize it in your mud, then perhaps not. But let me ask this: would this conversation make sense if we changed combat to crafting? WOuld anyone really support the idea that, instead of being told you have 10 pounds of iron and you need 5 pounds to make a sword, you were instead told you have a chunk of iron and need a brick, two bars and a pebble? Sure, you can add those descriptors later on, but if you don't have information regarding what quantities are available, or what makes a brick, a bar and a pebble, you'll be doing a lot of really irritating experimentation.