The latest firmware update for the Kobo Forma gives the option to enable or disable the header and or the footer in KEPUB e-books. I own the Aura ONE and the latest firmware does not support the feature. It appears, for now, the feature is restricted to the Forma. Due to its unique design, the Forma’s firmware has features that are not available on other Kobo e-readers. The choice to enable or disable the header and or the footer is not one of these device-specific features and so I expect other e-readers will get it soon. It is a choice that Kobo should have supported long before but neglected.
Kobo has a history of neglecting basic features, e.g., advanced PDF support, exporting annotations, landscape reading (a feature only available on the Kobo Forma) and syncing personal documents to collections. The upside is that it is relatively easy to install add-on software, e.g., KOReader, and patch the device to get some unsupported features to work. However, many of these patches are hit and miss - it would be better if Kobo developed Nickel to support these features natively.