i do this alot, too:D like the :ah yeah, yeahhh!" and the "oh" after the "Sure there are things in the band" in One I Love from thier Sydney tour:) and not only coldplay, at the wembley show, dave grohl(foo fighters) says "watch him as he GO-" istead GOES, but ithink it sounds better:P live performances more fun because of the changes they make, i think.

In Viva La Vida I say "Are we human or are we dancer, becasue I'm on my knees, begging for the answer" just before the last chorus like in 4Music.

 

I do this ALL the time now too! Its just stuck I spose :D