Quote from Loroese
You should include a dislaimer that AHK is considered 3rd party software by blizzard so using it can cause the account to become banned. Whether anyone has actually been banned for it is another discussion but use of macros goes against the ToS and is considered automation of gameplay.
Blizzard is fine with AHK so long as it's just one ability tied to a button. Multiple abilities tied to one button is when they start to get irritated if a noticeable chunk of the community does it. (Thinking back to WoW with TBC and WotLK rotation macros. One button you can spam to do your entire job for you! Took them a couple years to kill that off.) In the end I imagine that they could really care less about what you're actually doing, but are more concerned with you causing issues with hardware and software with the psuedo spamming. Most hardware has some form of a debouncer either mechanically or in software that keeps actual spam pretty low regardless of how fast you actually push the button. AHK basically bypasses that and that very bypass can cause issues.