I've gone through different phases of this as a tool to fight my ADD impulses. My main reason was to avoid that scenario where I would find myself reading and then snap and ask myself "where the hell am I in this paragraph/page/article?" I highlighted sentence by sentence as I read through, but it results in too many iterations. Then I highlighted whole paragraphs, worked better but reading through blue colored background when there's white background all around it made my eyes drift away to the lighter areas. Now I'm highlighting the paragraph prior to the one I'm in, it serves as a bookmark of sorts. It's still a work in progress but its damn better than not doing it!
