I've had a few anonymous comments on Dreamwidth that turn out to be from LJ people I know. You don't have to be anonymous if you're logged in to LJ. Here's what you do.
Log in to LJ, but then go to a Dreamwidth comment page.
Pick "OpenID" and enter exampleusername.livejournal.com (but use your name, silly).
Write and submit your comment, and LJ asks you to confirm.
If you say yes, your comment is submitted to Dreamwidth, and I can see who's talking. 8~)
This works on other sites too.
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