"We feel the script lacks primary colours." (the writer in question says "My offer to specify in the directions that the main character dresses in a pillar box red pullover throughout failed to retrieve the project from the bin").
"We like the writing but we're not doing grey" (as Oli has suggested, is there perhaps a glut of execs with synaesthesia?)
"This is too intelligent for an ITV audience."
"Hattrick is not at home to whimsy."
"It's very very funny, but it begs the question 'why?'"
"It's great. We love it. The script made me laugh out loud. We're not doing it."
Email from one writer to another: "Well we got the notes from ITV and basically they don't want jokes about people, ideas, books, places, history, travel, cars, politics or things. So far in the script they have approved something about a meat auction."
And from a director about a script that was made: "I don't bother looking at the bits in italics" i.e. the stage directions.
UPDATE: James Moran says:
You can name me, because I still don't know who the guilty party was. When Severance was being sent out to production companies, about a week later some complete stranger returned a copy to the PFD office - they'd found it on a bus. Clearly somebody at one of the companies found it a very gripping read. We never found out who it was, nobody owned up to losing it.
I would add to this, to continue the developing sub-theme of mystery rejection, James's agent rejected my very first sitcom script without me ever having sent it to him. He returned a copy of the script with a very nice note saying it wasn't quite his cup of tea, but I shouldn't let this kind of thing get me down, because everyone has differing tastes, and I was bound to get representation eventually, which I did, awwww. Although I still have no idea who sent him my script.