Perhaps this:
If you do not have your message boards enabled, and don't want to enable them, you can use your Calendar view to navigate to the Read Comments page for the entry you would like to mark as a memory . (If you have not enabled comments on your journal, people will still not be able to comment on your entries, even if they visit this page.) For information on how to use your calendar to locate entries, see http://www.livejournal.com/support/faqbrowse.bml?faqid=70. Finding and clicking the red heart button, as described in the previous paragraph, will take you to the "Add to Memories" page.
Should be changed slightly to something like this (changes are in bold):
If you do not have your message boards enabled, and don't want to enable them, you can use your Calendar's monthly view to navigate to the Read Comments page for the entry you would like to mark as a memory . (If you have not enabled comments on your journal, people will still not be able to comment on your entries, even if they visit this page.) For information on how to use your calendar to locate entries by the month they were posted in, see http://www.livejournal.com/support/faqbrowse.bml?faqid=70. Finding and clicking the red heart button, as described in the previous paragraph, will take you to the "Add to Memories" page.
This is because that when accessing the Calendar, a user is most likely to view the day view for entries, which does not provide a means of accessing the comments page of entries unless they have comments enabled. The user needs to view their entries by the month so that they can access the comments page of the entry they want to add to their Memories.
Any thoughts?