Meaningless Field Shadings In Documentation

Almost all of the guides have numerous, what I describe as, "Meaningless
Field Shadings" randomly dotted around them.

    *Eg:*

These shadings have no document fields associated with them. Other than
when I paste from a web page, I never see these shadings in my own
documents. So I assume these are some kind of indicator to the existence
of codes not used by the document.

Questions:

1. Does anyone know where these originate from?
    More importantly:
2. In the process of revising chapters, can we safely remove them?

Dave