Here’s the WaPo header: Put a lid on it, folks: Flushing may release coronavirus-containing ‘toilet plumes’
The idea is that if an infected person poops into a toilet, toilet plume (remember Cecil’s column about it?) from the flush causes virus-carrying aerosols to be propelled a few feet in the air, where they can linger until the next person uses that stall. And that person might inhale the aerosols.
It appears that the risk of transmission by this means is unclear, but probably relatively low.
But the proposed solution - closing the lid before flushing - seems out of place. That may work at home, but you’re breathing the exhaled air of your family members or housemates all the time anyway. And public toilets rarely have lids. So if one’s worried about this means of transmission, really the only remedy is just not using public toilets while out and about, unless you’re absolutely desperate.