Are there any features present in body text that aren't present in labels?

[galen]

The lack of punctuation suggests some aspect of the text may function as a 'separator' between one thought and the next. 

Since labels don't need punctuation,
if there are any properties of body text that are absent from label text,
they'd make compelling candidates for playing the role of punctuation.

What has been noticed about the differences between body text and label text?