what do you mean by "branle is not for blog post"? there is a client-side character limit on every note created on branle, but that doesn't prevent branle from displaying larger notes. and I think it is better for everybody is comments on a blog post can be made from branle.
Discussion
and even though these comments were made inside branle they are addressed directly to the "main source", i.e. the blog post event itself published by the original author -- instead of what happens today (many people tweet links to a blog post and people comment on these tweets).