一句呵呵让多少人心灰意冷
[yī jù hē hē ràng duō shăo rén xīn huī yì lĕng]
'A single 'hehe'(often translated from Chinese onomatopoeia as a casual laughter/contempt) lets many hearts down'. In the current online context, the seemingly light-hearted reply can carry indifference/dismissiveness, thus causing letdown or disheartening people. Implies how a carelessly thrown out reply can have unintended serious impacts on others