You claim people never asked promotions to be moved into a separate folder. As a user of Gmail, this is one of my favorite features. I'd first like to address real emails, like for instance from my mom, and then, if time permits, look at promotions. It's EXACTLY how things should be
It's also controlled by users. You can configure which categories you have and shuffle your mail around as you like-- I file blog posts under "Forums".
I never liked that gmail "feature" and disabled it as soon as it came out. It's stupid and takes away my control of my email. If I want some emails to end up in a specific folder/tag, or be marked as read, or even not show up in my inbox, I create a filter. I'm old enough to organize my email myself, thank you very much.
I had created so many custom tags and nests of tags and rules before their folder system came along that I never got the Google folder system, even to this day. For which I am insanely thankful. Apparently they figured I was already handling it and left me alone.
Why can't you just ask the reader to add the "From:" email address used in blog emails to their Contacts at the time they sign up for emails? Don't emails with recognized "From" addresses end up in Primary by default?
