A snowball thrown in either direction through a Nether portal is transported to the opposite dimension. A demo world is attached as "Projectiles through portals.mcworld".

Steps to reproduce:
(If possible, have a helper observing on the Nether side. Otherwise you will have to go through the portal to observe the snowball after throwing it.)
1. Load the demo world and get into Creative mode. If a helper is available, position them in the Nether.
2. From the Overworld throw a snowball into the portal.
3. If no helper is available, go through the portal and look at the bottom of its frame.
4. Repeat the experiment, but throwing from the Nether side.

Expected results:
The snowball goes through the portal effect without interacting with it. It breaks on contact with something on the other side.

Actual results:
The snowball is transported to the Nether and rests at the bottom of the portal frame. It remains a projectile entity. After about a minute, it disappears.