EDIT never mind. I kept reading posts and eventually the system added me to trust.
For others, just keep trying. I think clicking on posts is not enough. You actually need to “read” through them all too… or at least scroll slowly enough LOL
for anyone who is new and can not post, read above.
ps - I logged into existing ubuntuone account. I did not get any email at all explaining about the trust level or when I am eligible to post. So something may not be working correctly for new users.