Since Minecraft 1.8.8 came out, Some Items with health atributes are not stacking atributes correctly (Confirmed with Health attributes). This may be intentional, but it definetly doesn't look good right now.

I have recorded a video which graphically shows an issue with additional health point attributes stacking:

https://www.youtube.com/watch?v=PCH1qNJZk0k

Instead of accumulating additional health, the behaviour is quite inadequate, as when you wear two +10health armors, the total value doesn't ascend to +20health, and furthermore, when you pick a hotbar item with another health ammount, it overwrites the armor health to whatever the health ammount of the item you are holding is. When you stop holding a specially attributed item, all additional health goes away, completely ignoring the health your armor should give you.

(Items for this example have been generated with a Plugin, but the issue is just the same if you generate them on a Singleplayer Vanilla world with command blocks.)

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ADDITIONALLY: I think Item atributes need some more attention during Minecraft development.

I know these features are secondary, and only meant for Map Makers to mess around with (Also keep in mind that server admins like me like to offer these features to players to play with.) but they could definetly do with some optimization and additions.

Giants are another background Minecraft feature which has been lacking any love (Why not just directly remove them? You are making them more useless in each version, This can't be Notch's legacy...)

Please keep in mind what I say when it comes to Minecraft secret/background features. I think they can be kept simple, but please don't torture them more