The structure of what I had in mind was going through a laundry list of aspects of code (functionality, style, structure, functional decomposition, algorithmic efficiency, test coverage, use of libraries, blah blah blah), and making specific positive comments about the things that are already good. Personally I don't glean much value from that i.e., the compliments aren't something I'm concerned with and the feedback isn't something I can act on anyway.