could be because emoji are in the 'Miscellaneous Symbols and Pictographs' Unicode block, but the hourglass symbol is in 'Miscellaneous Technical', so it doesn't

could be because emoji are in the 'Miscellaneous Symbols and Pictographs' Unicode block, but the hourglass symbol is in 'Miscellaneous Technical', so it doesn't count as an emoji according to HN's filter