Ironclad is, I think, on the right path. The line is actually "Man is the cemetery for un-lived life". On its own, it is a condemnation (or accusation, if you will) of those who fail to live life. In the grand scheme of the album, it is probably about those who surrender to the inevitability of their own deaths. More on why in the essay above.
I wrote an extended essay on this album, available here:
http://www.ultimatemetal.com/forum/dark-tranquillity/570365-void-you-technical-reference-3.html#post9070729
Ironclad is, I think, on the right path. The line is actually "Man is the cemetery for un-lived life". On its own, it is a condemnation (or accusation, if you will) of those who fail to live life. In the grand scheme of the album, it is probably about those who surrender to the inevitability of their own deaths. More on why in the essay above.