The Bug:

Nether portal blocks cannot replace any replaceable blocks when creating a nether portal.

The only replaceable blocks that nether portal blocks can replace are fire and soul fire.

Steps to Reproduce:

1. Build the frame of a nether portal.
2. Place a snow layer inside the frame.
3. Attempt to ignite the nether portal.

Observed Behavior:

Nether portal blocks cannot replace any replaceable blocks when creating a nether portal.

Expected Behavior:

Nether portal blocks would be able to replace all replaceable blocks when creating a nether portal.