It is proper Netiquette for contribution of comments on other blogs. Do read and contribute to other blogs.
Contribution Netiquette Blogging
Blogs may allow written feedback. There are good reasons to allow it. There are technical reasons to prevent it. Spam feedback can lower rankings based on the url of the poster. Genuine feedback is generally welcome.
Comments are feedback on a given blog. They are the opinion of the commentator. Knowing what readers think of your writing can influence future posts. Good feedback encourages more posts. All feedback increases a blogs rank because it links more content to the blog. It helps to get feedback because it increases your blog ranking and makes you a better writer.
Commenting on other blogs is customary if you are a personal blogger. Blog commenting starts threads, discussions. A reply to a comment is a thread. Threads are comment discussions in posts. They attract new readers, engage an audience, and bring up new issues to blog about.
Comment on other blogs because it supports the community and attracts new viewers.