You can hack palm tree saplings as if they were still coconuts. When the sapling is hacked nothing actually happens. No sound no coconut halves are dropped nothing.
Steps to Reproduce
Plant a coconut. Hack the palm tree sapling.
Plant a coconut. Hack the palm tree sapling.
A developer has marked this issue as fixed. This means that the issue has been addressed in the current development build and will likely be in the next update.