That's a reference to the Sesame Street song ("We All Live In a Capital I") upon which "I" and "Imitosis" are, at least to some extent, based (or rather inspired).
Considering the egocentric connotations of a capital I (and the bleak, cold selfishness of the worldview in "I" and "Imitosis"), something being bolder than the capital I implies that it is some calling or quality than mere selfishness. It meshes beautifully into this love song (and reconciles or perhaps overpowers the themes of "Imitosis").
"in bolder letters than the capital I"
That's a reference to the Sesame Street song ("We All Live In a Capital I") upon which "I" and "Imitosis" are, at least to some extent, based (or rather inspired).
Considering the egocentric connotations of a capital I (and the bleak, cold selfishness of the worldview in "I" and "Imitosis"), something being bolder than the capital I implies that it is some calling or quality than mere selfishness. It meshes beautifully into this love song (and reconciles or perhaps overpowers the themes of "Imitosis").