First, I can't find a definitive answer on this, but has Nanovision been changed since the Beta? It seems to me I used to be able to see cloaked enemies/hunters semi-clearly (but good enough to use) with a bright transparent blue effect. Now it looks like a faint light blue blur that will get you killed when you try looking for that invisible enemy with the function that's supposed to detect them. And now there's no cloak tracker to make up the difference, not that it ever worked very well either.
Second, and this has been touched on though not thoroughly discussed, but WHY doesn't foliage/tall grass hide you in campaign? It's a major missing feature of the series, both Crytek and their now Ubisoft-owned licence of Far Cry. This was available in every Crysis iteration and should be in C3 (an expansion of C2 in the 'Warhead' sense of the word, as it feels/plays exactly the same/has the same glitches in it that Crytek were already aware of and confirmed but are still present, lack of new weapons/reskinned models ect...) The "Hunter" theme was seriously marketed/played apon in this game, even including a bow! So it makes no sense to remove one of the features that's almost essential and present in every Crysis to play the hunter!
Now and I looked on YouTube/Google for it but haven't been able to find either forum talk or a video of an easter egg I found. There's a Ceph Grunt standing between a dumpster and a long drop in the first group of enemies during Only Human. You'll have to sneak up to this Grunt or it'll be out of position to pull it off. If you (power kick module? I was using it at the time.) kick the dumpster into the Grunt, knocking it off the building (got alot of distance with him, maybe that's the trigger too.) A message comes over the radio in the form of a cliche soundboard effect of a crowd cheering/clapping behing Psycho saying "That's how you do it." Also take out the Ceph artillery towers in an order that ends with destroying the first one you come across in the level for some banter between Psycho and Prophet.
TL,DR
No wait- Everybody reads pretty fast nowadays. This isn't the 1800's, just read it! Takes less than a minute and a half if you do it slow, I clocked myself. Don't judge me...