Hmm, while we're here, it might be good to add some subsections to [expr.prim.lambda]; that subclause is a sprawling mess that's grown without any cleanup. Perhaps something like:

• Closure types [expr.prim.lambda.closure]: paragraphs 4 (everything except the specification of the type of a lambda-expression), 6, 7, 8, 21, 22, 23
• Captures [expr.prim.lambda.capture]: paragraphs 9-20, 24, 25, 26

... with the remaining text left in [expr.prim.lambda] itself. I'd also like a better description of closure types, perhaps first enumerating the different kinds of members that a closure type has and then describing those members and their properties.