hideParticle command doesn't work

Incorrect tag. Its ShowParticles.

Example:

/effect @p speed 20 1 ShowParticles true

Uh, no, It's not.

http://minecraft.gamepedia.com/Commands#effect

ShowParticles
Option to show or hide all particles for a potion effect, while the 'Ambient' tag only shows fewer particles. Set to true to show, false to hide.

Was introduced in 14w06a

On the minecraft wiki, it says that the command is hideParticles, not showParticles. I tested both anyway, with all combinations of capitalization, and none worked. So either way, it is still a bug.

It's not hideParticles or showParticles , it's true or false

hideParticles (optional)
Specifies whether the particles of the status effect should be hidden. Must be either true or false. If not specified, defaults to false.

/effect @p speed 20 1 true

Oh, I read it wrong. Sorry.