According to RFC 2646, the text

      `Take some more tea,' the March Hare said to Alice, very
      earnestly.

      `I've had nothing yet,' Alice replied in an offended tone, `so I
      can't take more.'

      `You mean you can't take LESS,' said the Hatter: `it's very easy
      to take MORE than nothing.'

can be encoded as

      `Take some more tea,' the March Hare said to Alice, very*
      earnestly.*
      #
      `I've had nothing yet,' Alice replied in an offended tone, `so*
      I can't take more.'*
      #
      `You mean you can't take LESS,' said the Hatter: `it's very*
      easy to take MORE than nothing.'#

(using '*' to indicate a soft line break, that is, SP CRLF sequence,
and '#' to indicate a hard line break, that is, CRLF).

Putting the encoded text into a buffer and issuing M-: (fill-flowed)
gives me:

      `Take some more tea,' the March Hare said to Alice, very
      earnestly. `I've had nothing yet,' Alice replied in an offended
      tone, `so I can't take more.' `You mean you can't take LESS,'
      said the Hatter: `it's very easy to take MORE than nothing.'

Using the attached patch, I get:

      `Take some more tea,' the March Hare said to Alice, very
      earnestly.
      
      `I've had nothing yet,' Alice replied in an offended tone, `so I
      can't take more.'
      
      `You mean you can't take LESS,' said the Hatter: `it's very easy
      to take MORE than nothing.'


I haven't thoroughly tested the patch to see if it has any unintended
side effects.

-Mark