Frances Bell

Is this when you have clicked to the forum from a 'See this message in context' in an email?  If so just use the 'breadcrumbs' - for this post here that is in yellow band at top of page with >> between levels, and click on the name of the topic.

Has this happened repeatedly?
I don't understand what has happened - maybe more information would help your question be answered.

I am only using groups for the first time so this is a guess - (Set to Groups visible) If student A in red group makes a post, Student B in blue group will be able to see the post but not reply (only to posts from other blue group members).
Alternative suggestion, post this question in Groups forum.

I have found that users don't always read the introductory paragraph.  A supplmentary approach can be to put your important message in a resources glossary with a suggestive concept name that is likely to invoke auto-text linking in the posts.
I have seen nudgin on some forums by posting a blank reply to push the post to the top but that's labour-intensive and a bit irritating to other users.
Stickyposts would be a good idea though.

Just had another thought provoked by something that Bryan Williams said low down in this thread.  He talked about the use of blogs and RSS.  I was envisaging a social practice that might emerge where people took topics about which they had a passion to their blog soap box, and people could opt in by subscribing to the RSS.
Now I may be wrong but I think that Moodle's RSS jumps over any privacy restrictions imposed on a course.  I mean that even if the space was not open to guests, blogs and any RSSed forums could be fed to desktop aggregators OR a public web page.
So to summarise, as well as Open to Google, guest access, we also need to think about whether forums have RSS and how blog use can be supported.