There's 2 different compatibility topics that are usually mixed up

either

a) Your addon can not use all of the features that are supplied by another mod/addon.

or

b) Your addon can't work/initialize, when a certain mod/addon is loaded.

Incase of a) this is not really incompatibility IMO, this simply means there are specific properties required to make certain (advanced) systems work with your addon.

Incase of b) this is imo really a compatibility issue, as your addon (or at least the system initialization) will not function at all.

for b), Solus and Killswitch designed XEH (Extended Eventhandlers) for ArmA1, and we took that to the next level, and extended on that with CBA for ArmA 2,

which a great many addon makers and mod teams have adopted, including ACE.

So basically what i'm saying, is that to be "ACE Compatible" or maybe better called "Community Compatible", one would have to be "CBA" or at least "XEH" compatible.

And to be able to USE some of the (advanced) features of the Mod, with your addon, you would have to apply certain properties.