Well, it is not bugs, it just exploits.
1. Sound cheating. AFAIK, there was one discussion, where KK stated that no sound can be assigned to nightmare creatures actions. In 0.9.9.7 I can set sounds for nightmare creatures, and it works!
Sound = {
   -- copy on imp entries
   nimp = {
      die         = "../doomrl_wavhq/dsbgdth1.wav",
      act         = "../doomrl_wavhq/dsbgact.wav",
      hit         = "../doomrl_wavhq/dspopain.wav",
      melee      = "../doomrl_wavhq/dsclaw.wav",
      fire      = "../doomrl_wavhq/dsfirsht.wav",
      explode      = "../doomrl_wavhq/dsfirxpl.wav",
   --   hoof      = "../doomrl_wavhq/dshoof.wav";
   },
   -- copy on demon entries
   ndemon = {
      die         = "../doomrl_wavhq/dssgtdth.wav",
      act         = "../doomrl_wavhq/dsdmact.wav",
      hit         = "../doomrl_wavhq/dsdmpain.wav",
      melee      = "../doomrl_wavhq/dssgtatk.wav",
   --   hoof      = "../doomrl_wavhq/dshoof.wav";
   },
   -- copy on cacodemon entries
   cacodemon = {
      die         = "../doomrl_wavhq/dscacdth.wav",
      act         = "../doomrl_wavhq/dscacsit.wav",
      hit         = "../doomrl_wavhq/dsdmpain.wav",
      melee      = "../doomrl_wavhq/dsclaw.wav",
      fire      = "../doomrl_wavhq/dsfirsht.wav",
      explode      = "../doomrl_wavhq/dsfirxpl.wav",
   },
   
   ncacodemon = {
      die         = "../doomrl_wavhq/dscacdth.wav",
      act         = "../doomrl_wavhq/dscacsit.wav",
      hit         = "../doomrl_wavhq/dsdmpain.wav",
      melee      = "../doomrl_wavhq/dsclaw.wav",
      fire      = "../doomrl_wavhq/dsfirsht.wav",
      explode      = "../doomrl_wavhq/dsfirxpl.wav",
   },
   
   -- copy of arachno entries
   narachno = {
      die         = "../doomrl_wavhq/dsbspdth.wav",
      act         = "../doomrl_wavhq/dsbspact.wav",
      hit         = "../doomrl_wavhq/dsdmpain.wav",
      melee      = "../doomrl_wavhq/dsclaw.wav",
      fire      = "../doomrl_wavhq/dsplasma.wav",
   --   hoof      = "../doomrl_wavhq/dsmetal.wav",
   },
   -- copy of arch entries
   narch = {
      die         = "../doomrl_wavhq/dsvildth.wav",
      act         = "../doomrl_wavhq/dsvilact.wav",
      hit         = "../doomrl_wavhq/dsvipain.wav",
      fire      = "../doomrl_wavhq/dsvilatk.wav",
   --   hoof      = "../doomrl_wavhq/dshoof.wav";
   },
   }
1. Color cheating. It definitely not a bug, but i decided to include this in my post. 
At first i used color.lua for painting regular stairs, because it always hard to find gray stairs amongst gray items and corpses, then i expanded it to other cells and valuable items. Like this:
Colors = {
        stairs_dark = LIGHTGREEN,
        stairs_light = GREEN,
        rstairs_dark = LIGHTRED,
        rstairs_light = RED,
        nukecell_dark = LIGHTBLUE,
        nukecell_light = LIGHTBLUE,
        barrel_dark = BROWN,
        barrela_dark = GREEN,
        barreln_dark = LIGHTRED,
        bridge_light = BROWN,
        bridge_dark = LIGHTGRAY,
        bbridge_light = BROWN,
        bbridge_dark = LIGHTGRAY,
        water_dark = BLUE,
        acid_dark = GREEN,
        lava_dark = RED,
        uparmor = LIGHTRED,
        upboots = LIGHTRED,
        udshotgun = RED,
        unboots = CYAN,
        umarmor = CYAN,
        udragon = LIGHTRED,
        uduelarmor = YELLOW,
        uballisticarmor = YELLOW,
   ubutcher = GREEN,
        unplasma = GREEN,
        unbfg9000 = GREEN,
        
        uoarmor = MAGENTA,
        ulaser = MAGENTA,
        bpack = MAGENTA,
}