When I researched the folding middle line last week (please see previous post for results on whether the middle line stood alone or linked the two halves of the poem) I also counted how often the title of the poem was used in the middle line.
I found that out of the 76 Folding Mirror poems on this site 10 had the full title in the middle line, 23 used parts of the title in the middle line, and 43 didn’t include any of the title in the middle line.