It's possible to /filter to an alias (instead of file-to file atm), and have this alias do some "text formatting".
But it's more easey (and might be sufficient) to loop all the lines of the sorted data (in this case: your file.txt), and e.g. write a text-formatted "ready-to-use" version to another file.
Something like (assuming $chr(61) as in the last example was your "separating char"):

Code:
[...filter to file.txt is done...]

  var %f = formatted.txt

  ; write heading lines
  write -c %f Total matches: $lines(file.txt)
  write %f $crlf
  write %f $crlf

  ; do something with the lines of file.txt and insert blank lines
  var %n = 1
  while ($read(file.txt,%n)) {
    tokenize 61 $v1
    write %f Nick: $1 Address: $2 IP: $3 eMail: $4
    write %f $crlf
    inc %n
  }

[...]

Note that you might use (hidden) @windows to "dump" and /filter data as well. I just wanted to demonstrate how /filter might be used to manipulate a dataset easily, if the data has been arranged on a line-per-line order.