For example, applying instant health (or any of the other instant effects) without a duration makes it last for 1.5 seconds instead of 1 tick, which means getting healed 30 times instead of once. Specifying the duration will convert seconds into ticks as per usual though, so the only problem is the default duration.
Comments 5
WAI
Not quite, at least if released versions of the game are any indicator; until now, all instantaneous-type effects applied through /effect if you don't set a duration lasted 1 tick (1/20th of a second). Also huh, interesting, looks like it is lasting 1.5 seconds instead of 1 second as you say... That actually makes me think even more strongly that this is unintended, because 1.5 seconds is 30 ticks, which looks to me like the effect command has been set up for a long while now to make sure instant effects are applied in ticks and not seconds. It's just that they forgot to set the default duration value to 1 for them with the new /effect, so it's still using the default 30.
Oh, nice! Didn't realize this got fixed last week until just now. It's missing from the list of fixes on the Minecraft pre-release page.
Default
/effectpotion duration is 30 seconds, divided by 20 is 1,5 seconds, wich evaluates to what you described. WAI