found a bug, the first one for me.

i was doing some testing on the effektiveness of ghillie suit. i was playing as a USMC spotter(has ghillie suit) starting about 100 meters from 2 Russian riflemen looking towards me, 1 was on Safe and one on aware. then i hit the dirt and started crawling towards them,
the one on aware would spot me about 10 meters away and kill me. I Tried again removing the one on Aware and started crawlin again but the guy on safe didnt do a thing. i crawled all the way to his feet. at one point he crouched down and started looking at me but kept his gun lowered. after touching his feet with no response from him i sat up. nothing, stood up, nothing, started to run in circles around him, he turned to look at me but didnt raise his gun to shoot me. then i started running away and still nothing.

however if i start standing and run towards him he shoots me alright.

In night time it's even worse. if i run standing up he will shoot me at 5 meters distance but if i run crouched down he wont shoot at all in any cases whatsoever, even after firing my gun.

EDIT: if i close to him but not directly towards him he will spot me sooner or later and engage but when moving straight towards him he does nothing but sit down and look at me.

I think this has to do with the lowered hearing of the AI in 1.03 IIRC...people were complaining that the AI could hear them too far away and kill them; so BIS changed it (albeit a little too low) and now they are almost def. Hopefully they or some modders can tweak it some more in the future

so based on the information that the AI behavior was changed in ACE2 i decided to repeat some of the tests.

i took a Chedaki rifleman and placed him in an open field with tall grass and few hundred meters away daytime and no ghillie suit they pretty much pick you up instantly.

the effektiveness of the ghillie suit is very changed. if your crawling slowly towards them with ghillie suit and they're set to safe they spot you at about 50 meters, with aware, a little more.

when lying still with the enemy moving towards me on safe they spot me somewhat later, maybe 15 meters. when on aware they spot me at about 25, interestingly if theres 2 enemies and only 1 of them is set to aware and the other one safe, the "safe guy" takes aim when the other guy does even before he has fired a shot. guess that means they communicate, they obviously weren't in the same group.

so if you wanna avoid getting spotted stay at least 15-20 meters away and DONT MOVE

in night time its a different story.
without ghillie suit against an enemy without NV goggles (Chedaki's)
on aware
crawling towards him he spotted me at about 15 meters
with him walking towards me ´he spotted me at 25-30 meters

with ghillie suit in nighttime:

enemy on safe crawling towards him, He sat down at about 10 meters but didnt fire. when i touched his foot he put his gun to my head and pulled the trigger

with them walking towards me on safe they aktually didnt spot me at all walking by 10 meters away.

so if you wanna play sneaky you need ghillie suit and nighttime otherwise they will spot you at some distance.