I very much agree that quoting from and adding something to a post is of great value, but some times I love something I don’t understand well enough to add value. That is why I’ve an enviable stuff category here.
For Micro.blog, I believe the right approach is to first introduce a simple “quote” feature. This UI would be streamlined to support quoting a sentence out of a blog post, with your own thoughts tacked on. It would fit with the spirit of easy posting in Micro.blog, but it would encourage more thoughtful posts and naturally scale up from traditional linkblogging.