The order of results should be the number of matches that it finds in the knowledgeable article text and collections. For example "the printer has fallen on another printer" would appear higher in the results list than "how can I make my printer make the tea" if you are searching on the phrase printer.
I wrote a document about this in Verity but some of this article isn't quite right for 7.4 so I will have a play around and see if I can write something for Lucene:
OK, but if you search on "Printer" and there are 200 matches that all find just one instance in the search fields but you know it was created in the last month how can you find without trawling through all 200?
The actual query arose because an Analyst here is search for a specific article "KB\123456". Lots of matches will be returned but they know the knowledge also fixed a similar Incident last week.
Sounds like an enhancement request to allow some sort of result sorting.
When I was an analyst I always used knowledge search when I didn't know the article I wanted (so I could search on some phrases and the KBS would search through multiple attributes for these phrases) but used a prompted article query when I knew there was a specific article that I wanted to find (as I knew what attributes I wanted to filter or sort on). But that's just me.
Yes it would need an enhancement request if you want KBS to behave more like a query.