1. Go to page http://www.livejournal.com/customize/options.bml and click link:
    Link to edit layer
  2. Insert this string property use view_comment_subject; into propgroup presentation:
    Add property to layer
  3. Press Save & Compile:
    Save&Compile
  4. Return to page http://www.livejournal.com/customize/options.bml and set Disable customized comment pages for your journal to Yes
    Disable customized comment pages for your journal
  5. Press Save Changes:
    Save&Compile
  6. Set Show subject in comment form for system style of comments to Yes:
    Show subject in comment form for system style of comments