In reply to Alimitch:
It seems to be "accepted practice" by many within the bouldering community. I've seen similar elsewhere - moving blocks, chopping down trees, etc. There's acceptable practice, and then there's crossing a line. It'd be hard to draw that line precisely, but I think we know it when we see it. Personally, unless we're talking about a futuristic first ascent, I think you get on with trying to climb something, or you try something else. If someone else has already climbed something, deciding you can't repeat it without first messing around as if you're trying to build your nan a rockery is a bit pathetic.