1st y is do follow important? Of course its very important. Without it mostly people don't want comment in your blog. Do Follow blog make people can make backlink with just comment in Do Follow post.
Now how to check a blog is No or Do Follow?
Use Firefox as your web browser and use this add-on.
After it installed then right click and left click at NoDoFollow.
Red link means NoFollow and Purple link means DoFollow.
Don't 4get to check my blog too