The main page of the Portal does limit results to the top 5 for both the Community and KBs. This is to keep the main portal page a bit cleaner and organized as results could be skewed to Community posts or KBs.
When you do searches on these pages in particular, you receive all search results for those areas.
So, this isn't a bug, it's by design.
Derek Curtis
COO
SmarterTools Inc.
www.smartertools.com