An error message should start with a capital letter but should not end
with a period.
+@item
+Many commands that take a long time to execute display a message that
+says @samp{Operating...} when they start, and change it to
+@samp{Operating...done} when they finish. Please keep the style of
+these messages uniform: @emph{no} space around the ellipsis, and
+@emph{no} period at the end.
+
@item
Try to avoid using recursive edits. Instead, do what the Rmail @kbd{e}
command does: use a new local keymap that contains one command defined