When you do the /effect command, it tells you what your arguments should be like this:

/effect <player> <effect> [seconds] [amplifier] [true/false]

However, in spigot version git-Spigot-87e2f47-ef13ca4 it only will show this:

/effect <player> <effect> [seconds] [amplifier]

When it should show if particles are show true or false.

/effect <player> <effect> [seconds] [amplifier] [true/false]

Besides that chat bug, there is no other issue so far with the effects themselves.