Dave Bauer and I have recently made some changes to the search on openacs.org, with the final goal to only index full threads instead of single messages, to avoid the cluttering of search results. It seems to work already for new threads - check this search:
http://openacs.org/search/search?q=powerbook+browse+compile+debug
note that the word 'debug' only occurs in the last message - previously search would not have found anything when the search spans the full thread.
What still needs to be done is to reindex all the old messages. I don't know why the abstracts are currently wrong, but after the reindexing that will be repaired.