In 1.8 when you tiped /gamemode 0 or /gamerule doMobSpawning false
it would appear in chat as:

Game rule has been updated
and
Your game mode has been updated

In the last snapshots Mojang changed it so that it told you which gamerule you changed and into which gamemode you changed such as:

/gamemode 0
Result: Your game mode has been updated to survival mode

or
/gamerule doMobSpawning false
Result: Game rule has doMobSpawning been updated to false

PLS ADD BCK IN !!!!