I'll try to answer as best I can, this will be written from a patient perspective not a clinician, so have that in mind.

I'm diagnosed with ADD which is treated successfully with d-amphetamine (3x 15mg daily). I will admit that I wasn't convinced at first about the existence of an "Attention Deficit Disorder" nor the treatment with stimulants, but that attitude has changed now.

To some extent the following:

1a. Identity disturbance: markedly and persistently unstable self-image or sense of self Yes definitely, because thought processes are usually very chaotic or caused by impulses, it makes it very difficult to keep a stable self image. Because you dramatically change your thought, with new impulses.

1b. And that identity disturbance is far worse than ADDer tendencies to hyperfocus or obsess over one thing then another thing? How to differentiate? Having the same thought for an extended period of time, is more difficult than giving in to impulses. So yes identity problems is definitely worse.

2a. Chronic feelings of emptiness Yes, this is caused by a combination of many factors. Largely caused because there isn't a stable self image, you don't know what you want because there is no "true" self. This makes any long term planning impossible, and allows only for living in the present, on the whim of your impulses. If you do try to look ahead, or at the past you will feel a lot of emptiness.

2b. Is it safe to say that chronic feelings of emptiness are far worse than the boredom that ADDers feel? How to differentiate? Boredom and emptiness go hand in hand, when you are bored, you begin to think. Which will lead to thinking about the future or the past, that makes you feel empty.

To a high extent based on emotional impulsiveness and rejection-sensitive dysphoria:

1. Affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability, or anxiety usually lasting a few hours and only rarely more than a few days) Very strong, poor impulse control leads to poor emotional stability.

2a. Inappropriate, intense anger or difficulty controlling anger (e.g., frequent displays of temper, constant anger, recurrent physical fights) Yes again, due to bad impulse control, you can easily react with anger. That can be physical fights or shouting/cursing etc.

2b. Is there supposed to be a difference between the anger, impulsivity or irritability that ADDers and borderlines feel? Don't know for sure, but anger of someone with BPD is usually internalized, while someone with ADD is more likely to be externalized. This can be either a physical fight, or yelling/cursing.

2c. Could it be that an ADDer with anger problems doesn't necessarily fit the BPD anger criteria because the BPD anger criteria is actually related to fear of abandonment? I mean it just says anger. I don't see anything in DSM-V saying that all or some of those criteria must be under the context of fear of abandonment. is there? Anger from ADD has more to do with the chaotic mind, and loss of control. Not really fear of abandonment, so yes it could be the difference with BPD.

1. Transient, stress-related paranoid ideation or severe dissociative symptoms I can't say this happened to me, but a lack of identity might cause dissociative symptoms.

And almost definitely based on DSM-V itself

1. Impulsivity in at least two areas that are potentially self-damaging (e.g., substance abuse, binge eating, and reckless driving) Impulsivity is the hallmark of ADD/ADHD, so yes definitely

This will be oversimplified: the mayor difference between BPD and ADD is most likely the cause and effect.

Does poor impulse control lead to poor emotional stability, then it's more likely it's ADD. Does poor emotional stability lead to poor impulse control, then it's more likely it's BPD.

With BPD there is usually a past trauma, which is the cause for the emotional instability. While ADD is something a person is born with.