chosenfire28 linked to this fix, and I thought I should help spread the word:
A journal style with comment pages fairly similar to the old one:
1 - Make sure the community’s account level is either Plus or Paid.
2 - Switch the community’s layout to Minimalism - Georgia.
3 - Go to Customize your theme -> Display and ensure that the “Disable customized comment pages for your journal” option is checked “No.”
Ta-da! It’s not perfect, but you’ll have comment pages that look like the old ones, and you’ll have subject lines.
EXAMPLE SOURCE