People come to your blog out of choice and not any compulsion. If you remember this, the rest is not important enough.
Respond with personalised comments rather than a generic Thank You. Fostering a conversation helps build the credibility of your blog!
E-commerce bloggers can gradually choose to write curated content from other websites/blogs. That always helps because a buyer will generally not spend much time surfing. He/she will appreciate it if you provide most of what they are looking for.