Odd, I can `C-s` just fine in transient buffers. It works exactly like in other buffers.

The `C-h` override is pretty cool there too, e.g. if from magit-status I do `C-h -D` (because I'm wondering what "-D Simplify by decoration" means), then it drops me straight into Man git-log with point at

       --simplify-by-decoration
           Commits that are referred by some branch or tag are selected.

(Ooh, I learnt a new trick from writing a comment, who say social media is a waste of time)