References:

  1) man-pages(7) from package "man-pages" or
"www.kernel.org/doc/man-pages" section 7 or
"man7.org/linux/man-pages/man7/man-pages.7.html":

"New sentences should be started on new lines.
This makes it easier to see the effect of patches,
which often operate at the level of individual sentences."

  2) groff_diff(7) in package "groff":

"In GNU troff, as in UNIX troff, you should always follow a sentence
with either a newline or two spaces."

  3) "info groff":

  Search for the word "sentence" in the output to get more hints about input
conventions.