I think we need to look at the highlighting feature from 2 perspectives: the author’s and the reader’s. What you have said makes sense from the author’s perspective (and I agree). However, in my experience (and the perspective from which Ravi was writing) is that simply highlighting does increase your followers — provided it’s done with due care and diligence. While I have no direct evidence of this, I can’t believe that my following (currently 13.6k) came from my stories and commenting alone.
Here’s another thought: the collection of a reader’s highlights — even if he or she doesn’t write much — is an insight into what makes them tick. This collection shows what’s important to them.
Before I follow someone, I look at what they’re writing, who they’re following and what they’re highlighting. Just by scanning through their story highlights, I can quickly tell what their worldview is, without having to read everything they’ve written, since a highlight more often than not equals agreement. I look at the title of the original story as well as the the actual words they’ve highlighted. There’s definitely meaning in what I find.
Just my perspective and response.