this is actually what I even assumed to be original request was, because it's what makes sense. I don't want to know every comment Denise makes everywhere, but I can see wanting to know every comment Denise makes in a particular news post. Besides, you can already track comments to a post, so this is basically tracking comments to a particular post with a filter added on top of it. I think that if you did it this way it wouldn't be a particular privacy issue at all.

But every comment a particular user makes anywhere, in the whole of dreamwidth? Yes, that would be a huge privacy issue.