The bug
Slow falling is considered a negative effect. I would have expected it to be a positive effect, because it prevents you from taking falling damage.
To reproduce
Run
/effect give @s minecraft:regeneration
Note that the effect icon is displayed in the upper row with the positive effects
Run
/effect give @s minecraft:slow_falling
The effect icon is displayed in the lower row with the negative effects
Linked issues
is duplicated by 1
relates to 2
Attachments
Comments 4

Relates to MC-84661.
the conduit power is considered a negative effect also
Yes, that's what MC-128321 is about.
Not fixed in 18w14b.
Edit: The potion descriptions for slow folling are now blue instead of red, but the icons in the upper-right corner of the screen still are ordered incorrectly.