The bug
Blocks that need to be attached to another block, such as ladders, buttons, or levers, cannot be attached to honey blocks.
Affected blocks
Ladders
Vines
Glow Lichen
Sculk Vein
Torches
Buttons
Lever
Tripwire Hook
Bell
Coral Fans
Amethyst Cluster/Buds
Hanging Signs
Resin Clump
Steps to reproduce
Place down a honey block and obtain a block from the list above
Attempt to place the block on the side of the honey block
Observed behavior
Blocks that require support cannot be attached to honey blocks, and the block fails to place.
Expected behavior
Blocks that require support would be able to be attached to honey blocks.
Related issues
is duplicated by
relates to
Attachments
Comments

Honey blocks don't have a full block hitbox, so this is likely intended.

Soul sand doesn't have a full hitbox either, but it can still support blocks on top. Since honey blocks render as a full cube this is without a doubt a bug.
Can confirm in 20w49a.
Can confirm in 20w51a.
Can confirm in 21w03a.
Can confirm in 21w06a.
Can confirm in 1.16.5 and 21w08b.
Can confirm in 21w13a.
Can confirm in 21w14a.
Can confirm in 21w16a.
Can confirm in 1.17.
Can confirm in 1.17.1.
Can confirm in 21w42a. Here are some extra details regarding this problem.
The Bug:
Blocks that require support cannot be attached to honey blocks.
Steps to Reproduce:
Place down a honey block and obtain a block that requires support, for example, a ladder.
Attempt to place the ladder on the side of the honey block.
Take note as to whether or not blocks that require support can be attached to honey blocks.
Observed Behavior:
Blocks that require support cannot be attached to honey blocks.
Expected Behavior:
Blocks that require support would be able to be attached to honey blocks.
Can confirm in 1.18.1.
Can confirm in 1.18.2.

A full list of blocks which can be attached to the sides of slime blocks, but not honey blocks (please include in description):
Ladders
Vines
Glow Lichen
Sculk Vein
Torch, Redstone Torch, Soul Torch
Buttons
Lever
Tripwire Hook
Bell
Coral Fans
Amethyst Cluster/Buds
Vines can exist if the main vine "plant" is supported further up, but the topmost vine of a plant cannot be supported by a honey block.
[media]

Solution, remove the ability to place all those things on slime so you all dont get confused.

...which is a TERRIBLE idea, introduces an inconsistency for no reason, and bars players from creating things they previously could that weren't a problem in that state.
Can confirm in 1.19.
Can confirm in 1.19.2.

Can confirm in 1.19.3.
Relates to MC-149663

This is also true for the recently added "Resin Clump"

Can confirm in 1.21.4.