So far just 3-4 at this point, some I guess figure out what I try to do when I ask for their company name and HN username, none of them been YC companies so far AFAIK. I don't know why they send specifically me emails, I guess either some automated system or they themselves see I spend way too much time on HN already, maybe just based on the amount of comments, I do have quite a bit of free-time :)