The bug
There's no subtitle when clicking a sign that has been locked by a honeycomb. When interacting with a sign, all sound events have their subtitles, like placing signs and using ink sacs on them, but the new sound doesn't have it.
How to reproduce
Place a sign
Use a honeycomb to lock it
Turn on the caption in the settings
Interact with the locked sign
What is expected
The sign makes a sound that signals it has been locked, and a subtitle appears on the bottom right.
What do we get
Only the sound is produced, but no subtitle appears.
The subtitle was added, but it still isn't actually displayed. New issue tracked at MC-261609.