List flag: crush-blanks

If set, multiple consecutive empty lines in submissions to your list
(and hence the digest and archive) will be reduced to a single empty
line.  Here, an "empty line" is a block of text delimited by
end-of-line characters which contains either nothing at all, or
contains only whitespace characters (space, tab, form feed, etc.).
If this flag is on, the first instance of such a line is copied normally,
but all others are ignored until a non-empty line is encountered.

If not set, all lines are copied as-is to the list and to its digest
and archive, regardless of whether or not they are blank.