LEARASHI

Your openID! Basically you could comment even without a DW ID by using another website (LJ in our case.) So when you have imported every post/comment from LJ, you have imported them with your openID, which means that posts you made in a community (= not your own journal) and every comment you've ever made will be posted as yourusername.livejournal.com and you can't edit them in any way until you claim your openID with your DW account, thus 'merging' the both of them. It's very easy to do, and can be useful in the long run, because if you delete your LJ for any reason, you can still edit previous posts/comments you imported on here! Here's how you go about to do it: https://www.dreamwidth.org/support/faqbrowse?faqid=84

Do let me know if you need any help! :D