"it was there."
Beware: can of worms opening; rant following... (not directed to Dave, personally, but to the idea he suggests)
"It was there" may have been good enough motivation for Mallory, but it is never a good reason to leave anything in a photograph. It never has been, even in the film days, and never will be. I'll grant that it's certainly a well-entrenched belief/philosophy/dogma, but it's not based on any legitimacy.
The two assumptions this notion is often based on are (a) Earth/Nature is static, unchanging; and/or (b) a photograph is a genuine reproduction of a scene (note the oxymoron). Well, neither concept holds any truth. The blade of grass, pebble or branch that's here today, could easily be gone tomorrow with a wind or a wave. The sign/post in Matt's photograph could also be gone tomorrow or painted over, or even replaced with a billboard. Nothing is static; there's no reason why we should think otherwise.
And photographs have simply never been nor ever will be entirely truthful to the scene they represent. They are entirely malleable through every step of the process. The photographer chooses a time, date, point of view, perspective, exposure, depth-of-field, etc., etc., so whatever they capture at that moment has already been manipulated. Look at the water in Matt's photograph – it's clearly not the way it looked; it was determined by shutter speed. Even the blueness is up for debate and can be changed. What if the sign were not removed, but simply darkened with a hue change to blend in? Would that keep the scene any more "honest"?
Bottom line: Why should a single object in the photograph be held in sacrosanct if the whole presentation of the scene is manipulated?