It's not completely their fault either. Although their engagement would harm your numbers. You never know why they are doing this. Yes, they are trying to earn some quick money. Yes, they could have also searched for something they genuinely want to read about. There are some caveats to that too. I feel most of us are not readers on Medium. Reading the full article also doesn't make you a genuine reader if he didn't read it out of interest. But yes, if they just click on your article read one or two lines, and add a comment it's sad(For them and for us). If Medium had allowed writers to earn from non-medium member reads or made Medium free for nonmembers to read the scenario would be different. Also, not everyone is that confident about their own writing or SEO skills, hence they resort to these behaviors. But I am sure they don't enjoy doing it too.