You might get more comments on your blog if you make this simple change. Disable the "capcha" type feature which forces visitors to type in a jumbled up code word before they can comment. I know that I have abandoned commenting on many blogs because the code is so hard to read and not worth the time.
You'll find that spam isn't an issue really, at least I never get any. Another wise blogger did a similar post to this when I started blogging and I was very thankful for the simple little tip.
Thanks for listening to my rant.