Highlighting issues in range queries

I use highlighting in order to prevent manually find what made the document returned for a particular query. But for some queries highlighting is not working.

1.) Range queries
When I do a range query with highlight request , the "matched" values between a range are not highlighted. Is this by design ?

2.) Must not query results
Words that are not matching are also not highlighted. (probably by design). Is there a way to force a highlight for each fields even if it's empty?