Easy and simple, commenting is all about being polite and not trying to grade the individual.
1)Be polite– try to give good and nice feed back to the person
2)Make connections– try to have links with the other persons post and see if you can relate with them
3)Add value– make sure you show how much you care and it is not like a short comment
4) ask Questions
How to comment on edublogs?
You go to your dashboard in the comment section, then click on the comment you want to reply on, and click reply. Next press enter!