Oh, so that's how it's done. Go to Customize options and set "Disable customized comment pages for your journal" back to "No". Comments will then appear in the style of your journal with no bar at the top, and with subject line, drop-down icon menu, and preview buttons intact. Thank you, juliansinger. (Then go to Profile-> Settings-> Display and tick 'View comment pages from my Friends page in my own style' so as to have those options available always.)
Mind it's still a piss-off, because I used that bar to let me post entries. Now I have to go to click User Info to get it. But for the comment options we've always had, it's worth it.
Oh, and a further pain if you want to edit, because the 'edit this entry' icon is missing from punquin and one must do it from the menues. ETA: or that tool bar at the top of the entry that I've always ignored. Ohh LJ, just give us back our commenting styles, will you?