Yeah, I'm pretty sure the option to submit journals is enabled. I'd just have to approve the entry before it's published.
And, in the case of something to be posted for the entire group to see, I'm going to be harsh in my judgement. While comments and stuff are fine for hating and ranting, etc, a public journal that will be in everyone's newsfeed is a different story.
I will maintain that what this group offers is love for the the series. Yes, you can have an opinion, but having an opinion and bashing are 2 very different things.
So. You can submit a journal. But whether I'll publish it is no guarantee, so do choose your words carefully. You can hate, but I won't promote it.