Hey there :)

This addon isn't working at all for me running WoW SL 9.2.7. (I reallize it hasn't been update in quite a while.)

But then again, using the normal supression commands (that your addon is a substitute for) isn't working either.
Did Blizz change anything on that regards or is there a way you can make it work for 9.2.7?

Take care :)

The macro I am using as an example:

#showtooltip
/dismount [mounted]
/su
/cast Glide
/su
/cast [mod:shift] MyUnderwaterMount; [noflyable] MyGroundMount; MyFlyingMount

Glide is Demon Hunter ability. It can only be using when being airborne and will result in a red text error message when trying to do while grounded. Using this macro (your addon) (or the standard error suppression commands) will still give the error message and not suppress it.