I have always thought that speaking the last line of a narrative song or saying the title at the end (often in a quieter voice than the song was sung) was of Irish origin and certainly seems very common to Irish singers. I had always looked on the latter habit as a gesture of acknowledgement to the "spirit" of the song.

I tend to sing in bars and singarounds and have been trying (unsuccessfully) to break myself of the habit of singing with my eyes closed and a hand cupped over my ear. The problem is, I like to lose myself in the song so singing like that puts me in a different space and lets me concentrate on (hopefully) doing justice to the song. So it is being done, in my case, for the auditory, not the visual effect (I'm much better if you can't see me – honest!).