OK, the 24-hour limit is now in place in the sections that people mentioned.
It seems
Marketplace (Altcoins) > Bounties (Altcoins) was forgotten, this was posted and deleted many times:
How can I use Exereum after?
Can you add this board to the 24h deleting restriction?
This was posted many times in
Pyccкий (Russian) > Aльтepнaтивныe кpиптoвaлюты:
Пpикoльнo, тaкoe peшeниe oчeнь yдaчнo, yчитывaя, чтo ИКO eщe идeт.
I'm not sure how often this happens on Russian boards.