The bug
The potion particles are not spawning in the middle of the block. They're spawning on the edge of the block. Does not happen when you use the following command with a command block:
/particle <particle> ~0 ~1 ~0 0 0 0 1 1
Code analysis
Code analysis by @unknown can be found in this comment.
Linked issues
is duplicated by 29
relates to 4
Attachments
Comments 37


Fixed in 14w05b.
Tested with
/particle mobSpell ~0 ~1 ~0 0 0 0 1 5
Please re-open this issue. The bug is still prevalent in 14w27b. No matter where you throw a splash potion, the particles only appear on the North-West corner of the block they landed on.

Reopened and confirmed.
Confirmed 1.8-pre1
Affects 1.15 and 1.15.1 pre-release 1.

Also Eye of Ender broken particles are offset.
[media]
@@unknown, that is a separate issue and I created MC-172739 for it and attached your video there.
Please comment on it if you want to become the reporter.

Affects 1.16 pre5
Resolved? in 1.16 Pre-release 6.
Splash potion particles now always spread from the center of the block, regardless of impact
Use absolute coordinates and add .5 to the end of the x and z coordinates. It's the only advice I can offer.