I expected the empty wooden bucket to stack with another empty wooden bucket. The empty bucket has "0 nbt tags" in its description and will not stack with other empty buckets.
Screenshots:

To Reproduce

1. Milk a willing cow.
2. Then empty the bucket by click on a barrel. This will NOT work by emptying the bucket on the ground.

Meta Info

• TFC Version: 1.2.1.44
  Can be reproduced in creative with a milkable cow and a barrel.

Duplicate of #946, but apparently still an issue.