On page 205 of Ch. 9, pdf Lilypond documentation for v. 2.5.19, a
"trick" is given for raising markup text. It appears, as it has in
previous versions, that the "raised" example has a null space ("")
rather than an empty space (" "). If so, it would explain why (at least
in the pdf version of the documentation) there is no discernible change
in position for "not-raised" and "raised".