Refer to the LTSD (License to Spell Doom) map you provided in the ATI Fog forum post.
When you find a monster that has "invisibility" (first chance you see them are the zombiemen in E4M5), using Light Amplification revealed them. In comparing this to ZDoom, ZDoom doesn't exhibit this.
			
			
									
						
										
						[It's a feature, not a bug!] Light Amp/Invisibility Bug?
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				Deathlike2
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