Thought it's some deprecated setting reverting to defaults at runtime but you know what it was? Searched my scripts folder for "SetINI" string and this is what I found: zbloodnpcquestupdatescript.psc (Enhanced Blood Textures mod)
function OnPlayerLoadGame()
self.updateEBTmod()
utility.SetINIBool("bDecals:Decals", true)
utility.SetINIBool("bSkinnedDecals:Decals", true)
utility.SetINIInt("iMaxDecalsPerFrame:Display", 800)
utility.SetINIInt("iMaxSkinDecalsPerFrame:Display", 250)
endFunctionSorry for bothering you but I didn't expect mod authors to change my INI settings just like that.