So I hate to break it to you all, but uhm... yeah... like, this forum is actually public. That means anyone who stumbles upon it has your implicit permission to read anything you write, because, you know, you wrote it on a public forum on the internet and stuff...
If you want to write things that are truly private, and control who has access, then setup a blog on Blogger and make it invite-only. Otherwise, you don't really get a vote in who is "allowed" to read it... You do not own your partners, and you don't get to tell them what they're allowed to read on the internet. If you put something on the internet that you'd rather they didn't read, that's really your problem and you need to think twice about what you write in public.
Just because you don't give the URL for the forum and your username here, doesn't mean your circle won't come across it. You're in a polyamorous situation. Each and every one of us found this forum while we were seeking information and discussion about polyamory. Is it such a stretch to imagine your partners might have the same desire? Once they find it, it's not terribly hard for people to recognize themselves in a blog, especially as you describe more and more people and situations.
For example, if you put something on a public forum, you no longer get to call it "a secret." It's like when people say something on the radio "just between you and me." The difference is they're being tongue-in-cheek and they have no illusions that it's not being broadcast across the world.
Furthermore, if you're blogging about other people and revealing details about their lives, they have every right to read those things. If they ask you not to post about them, it would be very rude of you to continue doing so. Thus, if you're posting things you believe they'd rather not have disclosed even anonymously, and you're worried that they might read it, then that's probably an indication that you should shut your mouth and keep their secrets to yourself.
All that being said, of course you have the right to request that your partners respect your space. But you need to realize that's a request on your behalf, not an obligation you can impose upon them.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker