When i was playing Multiplayer (which might of been the reason for this) i accedentally clipped through a cactus and i did it again after.
I thought it would just hurt me, but it also clipped me through.
for the 2x1 hitbox, i just noticed it, but when i tried to punch the invisible part of the hitbox nothing happened
1. enable flight or enter creative
2. fly down (maybe diagonally downwards) onto a cactus
3. you will be clipped through the cactus (but you don't get x-ray vision)
P.S.
i am not 100% sure if the server is 1.8 or 1.8.3
**I have found this to happen while i was in 1.8.6**
Thank you for your report.
However, your ticket has been resolved as invalid.
This ticket relates to a modified or 3rd party client, server, or launcher.
Any non-standard client/server/launcher build needs to be taken up with the appropriate team, not Mojang.
Any plugin issues need to be addressed to the creator of the plugin or resource pack.
This site is for addressing issues related to the base unmodded Minecraft; Bukkit, Forge, Optifine, modded servers such as The Hive, Overcast, Showbot, Hypixel or any other modded system invalidates your ticket, unless the behavior can be reproduced in Vanilla.
Additionally, if you have problems on large-scale modded servers, please report it to their site. It's probably not a bug in Vanilla Minecraft.
:info: If you are able to reproduce your issue in a vanilla environment, feel free to create a new ticket.