friends are saying they have to log in to respond to my plurk, why?

I'm not staff... but do you mean real life "friends" or "friends" in the plurk concept? The question is confusing as of course everyone has to be "logged in" to use plurk, which includes responding.

Maybe they see a reply box before being asked to log in? I've noticed some weirdness with what you can and can't see based on your logged-in/out state.