Since you ask ... Personally, I detest all forms of terminal manipulation, be it reverse video, underlining, fake bold, colorization, or what have you. For me, all such things merely distract from reading the content, which is what I'm interested in. (For me, this is the case for everything, not just Info files.)
Philosophically, I think there is a consistency, simplicity, and universality in making the defaults be "mode line in reverse video, everything else untampered with" which is lacking with any other policy. However, I recognize this is not a popular stance nowadays, , so I can only encourage you to do whatever you think is best for most users. Re the header line, I also have been annoyed by its spilling over to a second line, wasting precious screen real estate. However, hiding it completely feels somehow problematic to me. Maybe another option would be to truncate it at the screen width. Karl P.S. IMHO, hide-note-references (and all similar things in Emacs that effectively reformat the Info file) is a misfeature that shouldn't exist at all. Not that I expect that to happen. Certainly I think hiding should not be default.
