Horizontal spacing markup bug?

[Daniel Johnson]

I've noticed that when I have a long markup associated with a note, and
a short markup associated with a space occupying the same beat as the
note, the short markup is aligned along the center X-axis of the longer
markup.  I first noticed this with the piano centered-dynamics template,
but I've narrowed it down to the following code.  Is this a known
issue?  Surely I can't be the first to notice this.

%%% begin lilycode %%%
\version "2.5.26"
\paper { raggedright = ##t }
\markup { "The two " " " \dynamic "p" "'s below should be horizontally
aligned with each other." }
\score {
    <<
        \context Staff = voiceOne { c''4^\markup{\dynamic "p" \italic "
mezzo voce"} c'' c'' c'' }
        \context Staff = voiceTwo { s4^\p c''4 c'' c'' }
    >>
}
%%% end lilycode %%%