I remember very clearly when an editor for Science was asked about whether or not they would publish work if it appeared in a blog post, the editor replied with "so long as it has no more than 70 likes, 20 share, or 30 re-tweets".
She was actually being satirical, and ended up having to restate that Science doesnt care so long as "the core scientific message" is novel in their publication.
Truth is, I hear a lot of stuff like this from journals claiming to be all about the dissemination of science. What i DONT hear is people who's work was rejected specifically because of a blog post. Probably because the rejection letter is the same old standard "Better luck next time." and the real reason is never known.
Long story short, if you want to keep publishers happy, do whatever you can to make the article valuable...