lots of accurate RAW
thanks again, I agree with much of what you said here.Despite situational modifiers, however, the point is that the stealth bonus of said sniper in the open is not affected by their skill ranks, dex, gear, etc. which require cover or concealment, unless they have HiPS. HiPS, through some unspecified magical effect, makes these bonuses apply when they shouldn't. Special senses certainly prevent (visually based) cover or concealment from working, and although they don't "normally" need to make checks, their description allows that there may be circumstances in which perception checks need to be made. So it isn't absurd to require checks for unfavorable conditions (like loud ambient noise, strong smells, etc.) in the same way that one might make distracted players make perception checks against the distant sniper in plain sight against the sun.
So, if special senses aren't completely infallible, and are subject to at least some of the same limitations of normal senses, how can HiPS overcome the requirement for cover/concealment for normal senses but not special senses, unless it is visually based?