-skip over differences in states prefer-A and prefer-B (@pxref{State of
-Difference}). Thus you see only differences for which neither version
-is presumed ``correct.'' The mode line indicates Skip Prefers mode with
-@samp{S}.
-
-@findex emerge-auto-advance-mode
-@findex emerge-skip-prefers-mode
- Use the command @kbd{s a} (@code{emerge-auto-advance-mode}) to set or
-clear Auto Advance mode. Use @kbd{s s}
-(@code{emerge-skip-prefers-mode}) to set or clear Skip Prefers mode.
-These commands turn on the mode with a positive argument, turns it off
-with a negative or zero argument, and toggle the mode with no argument.
+skip over differences in states ``prefer-A'' and ``prefer-B''
+(@pxref{State of Difference}). Thus you see only differences for
+which neither version is presumed ``correct''. The mode line
+indicates Skip Prefers mode with @samp{S}. This mode is only relevant
+when there is an ancestor.
+
+@findex emerge-auto-advance
+@findex emerge-skip-prefers
+ Use the command @kbd{s a} (@code{emerge-auto-advance}) to set or clear
+Auto Advance mode. Use @kbd{s s} (@code{emerge-skip-prefers}) to set or
+clear Skip Prefers mode. These commands turn on the mode with a
+positive argument, turn it off with a negative or zero argument, and
+toggle the mode with no argument.