We don't show the active cell, as it originally did not look that important at least on Android. It is different in the browser where the user expects much more desktop-like behaviour - we should add the marking of the current cell. Should be painted on the client side, though support from the server will likely be necessary.
Andrzej Hunt committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=2bcaffd12263e8f3c2a2fbf8ccc4b9bba2642146 sc lok: tdf#94605 introduce uno:CellCursor It will be available in 5.1.0. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Andrzej Hunt committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=09e823e750a98a5cd7d504c4558016f8ce1b935b loolwsd: tdf#94605 handle LOK_CALLBACK_CELL_CURSOR
Andrzej Hunt committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=d9d0d47514fef09d0606abcf7dc48b6b977c8987 loleaflet: tdf#94605 Show cell cursor
Fixed now, thank you Andrzej!