"Sledging" happens at all levels of the game, but this, if true, sounds a step too far.
You used to see it on televised games a lot but I think players have got used to hiding it from the camera. When you see a player suddenly jump up out of a tackle fists clenched and eyeball the opposition it isn't because he's been asked the price of fish!
The Daley incident has been blown up out of proportion, mainly by a side who were desperately trying to hide their embarrassment at their own performance and were looking to deflect attention.
I think we should be more worried by players who run in third man leading with knees and elbows, or those who deliberately put fingers in eyes. One of the young upcoming "superleague superstars" appears very good at this and is either due a very long ban or a good hiding - not sure which will come first