Okay, I think I'm starting to understand how these bugs work.
If estsoft wasn't completely ignorant and incompetent, they could have fixed all 3 at once. I have to assume they didn't fix the root of the bug("the" variables), only did some fix related to weapons, so they won't write in those variables when in "red" status(which won't prevent other items/skills writing in the variables).
Your AA/DA doesn't change, becouse the stats of your char never changes(not even during using a skill), only the stats stored in the variables get added when calculating your damage if you attack something.
Now these guys said that your hp is not going up when using the epaulet method... Well I'm not entirely sure about that, it's probably just not visible, becouse it's valid only for that moment when you get attacked. So you stacked an epaulet 100 times which gives 350 hp, then you can't be killed, unless the mob hits more than 35000(+your original hp). It's just my theory, and hp doesn't even matter tbh, but imo additional HP is stored too and used when you are attacked.
I guess they already fixed this on EU servers, so no bug should work which is based on stacking "red" status items. Same should apply to skill stacking bug(which must be based on accumulating stats too, in those variables). But who knows...
This info won't help you find how to make items bugged, but can help you decide if you really want to invest time/money into this. Personally, I think all these damage stacking bugs will be fixed in the near future(if estsoft cares about it), so I wouldn't waste money to buy it or time to find it.
The guy who leaked weapon stacking fucked everything up. So gz to him.