First thing to do: check how your comments appear.
- If they're normal, don't do anything.
- If they're not, go to your "Customize Journal Style", verify it's in S2 style. [You can check if you have S1 or S2 at the bottom of the Theme bar on the left side
here....]
If it is (it should be), go to "Customize your Style" and to "Disable customized comment pages" say "No". [It's for all accounts. Go
here. Go down in the page to Presentation Basic Options and put "Disable customized comment pages for your journal" to "No"]
If it is not, you have to upgrade to S2 ^^"
If it doesn't work, it might be because you're in Basic account. Sadly this only works for Plus (and Paid) accounts [NOTE: Plus account is FREE!], so you'll have to upgrade. It only takes a few clicks but your LJ layout will most likely be lost.
NOTE: the change only applies for your own journal. The comment pages of the other journals/community you go to depend on their respective owner. I can only encourage you to ask them to make these changes.