Marco Cecchetti committed a patch related to this issue. It has been pushed to "libreoffice-5-3": http://cgit.freedesktop.org/libreoffice/online/commit/?id=a7a2578d4535e8d39dd0beac8a466f9d7f81f864&h=libreoffice-5-3 tdf#106598 loleaflet - calc: row/col header unproperly highlighted