Identifers for text and flashbacks
My wife and I have been watching your dramas every night for years. We are totally dependent upon English subtitles. Two things occur in every episode of every drama that are easily misunderstood: (1) The subtitle text when the actor is thinking to himself rather than speaking out loud, and (2) flashbacks.
Each of these should have a visual marker so that the viewer knows what he is seeing.
A visual marker for the subtitle text of the actor thinking to himself rather than speaker out loud is easy: just put the text in italics.
A visual marker for a flashback could be a different color -- B&W or a yellowish cast -- or even the word "flashback" displayed in the upper corner of the screen. Your technicians are surely more adept than me of finding an appropriate and workable visual. marker. I request that they do so.