OP, the simple answer is, it IS against the rules to use it. At any time you could be banned for it. So why take the chance.
The risk is up to you, but if you get banned for it, Blizzard was in the right to do it since the addon is clearly breaking the rules, no grey area about it.
Is it possible you might get the ban reversed? Yes, but know that Blizzard usually takes a few days to resolves these matters, so if you use it, get a ban and appeal it, you will be looking at several days without access to your account.
And iMorph can get another flag at anytime causing the whole process to repeat.
Ask yourself, is how some pixels look worth all that hassle?