A comment is important to a blogger because it lets them know what they might be doing wrong and what the people reading their blogs like.
Here are my tips to writing a good comment-
-State everything you like and found interesting
-Tell the blogger what you think they could do to make it even better
-Don’t pull out all the mistakes the author made, for it may make them feel bad
-You can also give suggestions of topics they should blog about, what you find interesting.
This is what I think you need to write a good, quality comment.