I think building an online education network, or joining one already in progress, can be a good thing to help provide growth for both students and educators. A PLN can be good because it is personalized and most relevant to those involved.
I think the most important advice about commenting is to write something meaningful. I like reading comments on various websites, yet sometimes people tend to stray from the topic, or they just type agreement statements, and it doesn't really add to or stimulate the conversation.
Blogs I have followed and commented on:
Planet Mongo (Kim Montgomery)
If Only Shakespeare had a Blog (Liz Edison)
11 Tools by Lindsey Braden
Mr. Maddocks Spanish Class (Andrew Maddocks)
Srta Kirklin's blog