Separate outputs on key down and key up, are only possible because the Warcraft Keyboard API acknowledges them as separate events.

If Blizzards API (which addons use) did not allow for events to be registered on press and/or release, then it would not register those events and no matter how we configured our boxing software -- one would be read and not the other.

It is a feature Blizzard specifically put into the game for addons to use, so you're not going to get into trouble when your software (which uses an addon, completely subject to Blizzards API, to generate the macros) can split events between press and release.




On spamming keys...
Sure you cannot macro IWT, with the Warcraft Macro Engine.

But you can keybind IWT to "4".
You can have a spell or macro on keys 1 through 3.
You can glue a popsicle stick across keys 1-4, and mash them all at once.

If an action is restricted to occur no more than once per time interval, such as every spell on the Global Cool Down... it will only fire off every so often, subject to when other actions have fired off.

Mind Freeze is off of the GCD.
We can freezly mash Howling Blast and Mind Freeze together (and if talented, Mind Freeze is Runic Power free... meaning it will be available to fire off on any press and then 10 seconds thereafter).
Only HB is on the GCD.

Interact With Target, like Mind Freeze, like /assist [target=focus], like "W" to move forward, like a lot of other actions is off of the GCD.
Meaning you can freely combine that keybind with another action as often as you like, and Blizzard does not mind this.
Under the current rules of the game, combining the IWT Keybind with another keystroke will not get you in trouble or subject your account to disciplinary action.




The key still being, everything you do is a result of something you push or release at the time it occurs.
Nothing is a result of something you pushed or released or clicked at some point previous to now.

If you search my post history, you'll find I've been using an IWT that has been integrated into my DPS spam sequences for close to a year and a half.
For eight months of the year, I'm often online for 12 hour stretches... so its not like Blizzard has not had opportunity to detect what I push and what it does.
I posted how to do this more than a year back, and can only assume others are using a similar technique.
No one has ever posted that they have been banned from use of IS Boxer (or other legitimate boxing softwares, at least to my knowledge).

Looking at the DK Manifesto (by Mosg2), it is assumed you will use IWT as an integrated part of your DPS.
The 4x DK + 1x Healer is probably the most popular team of the expansion.
The 4x Ret + 1x DK was probably the most popular team of the last expansion.
Both use IWT integrated into DPS Spam.
No one has been banned or suspended for this.
And a lot of users do precisely this.



As always use what you are comfortable using.

If Blizzard gives you a tool to use in their game, it is your option whether you want to use that tool or not.
If you are comfortable with it, then use it.
If you are not comfortable with it, then don't use it.

Bottom line.
It is a tool that Blizzard is okay with your using.
Decide if you want to take advantage of it, or not.

So far that means a boxing software such as HKN/IS Boxer, possibly others.
Or one of the addons that can send a different key output for Key Up and Key Down.