I agree Deborah - I got tripped up on exactly the same thing. Note my response back to you when you advised same issue. I fear many hosts and guests are going to be very confused now that everyone is lumped in together and has to try to work out which forums are for both host and guest, which for guest only and which for host only.
At the moment it's all by trial and error and this and mine were such errors waiting to happen.
The main loophole for error is using the search for a relevant string, reviewing the returns, and seeing nothing suitable simply clicking 'start a conversation' - there is nothing to tell you at that stage what group you are in or thereby posting too .......
Just as well this community forum is in beta test currently, and here's hoping airbnb will take note of common confusions and host feedback on such matters.