I have a little report regarding negating IFT effects: One can for example write IFT: !CUSTOM(test); ATK: 2 to allow a +2 attack bonus as long as the target has not "test" as an effect.
Now, there is some matter of preference regarding logic: It works, however, if one has no target, then the effect is not applied either. In my extension I rewrote it in such a way that those effects are also applied if there is no target (so negated conditional returns true). It is a matter of preference for sure :) But some might argue that it is more logical to say that the negated conditional of "If there is a target with "test" as effect, then apply +2 ATK." is "If there is no target with "test" as effect, then apply +2 ATK.", and having no target at all "trivially" means that there is no target having an "test" effect so that the bonus should be applied
(but that is nitpicking on logic; most of the time it doesn't matter, but I still wanted to report it in case you actually have a preference :) )
(The version of a negated IFT allowing no targets was a bit nasty to code though, in particular I had to consider what happens if it is a drag&drop attack and stuff like that; but the new code may not have the problems I had back then :) )
EDIT: Even if one reads this as "If there is a target and it has no 'test' effect, then apply a +2 atk bonus", then one could argue that "no target" means one has actually a target, an "empty target" interpreted as "target" naturally satisfying to have no "test" effect, and so it should allow a +2 atk bonus :D (but that is now how we mathematicians approach logic, so really just nitpicking here :D)

