I should think so, pretty sure I've seen others with them though that that may have just been ridden hunters...
Its probably to do with fashion and cost (aren't they quite expensive?) as to why more people don't use them as I can't imagine it would be incorrect for WHP...
ahaha no there was a hoof pick and haynet in there too so hopefully be ok!!!! lol. i cant believe they didnt mention the whip in the listing they would probably got a lot more bids if they had! mind you i havent had it yet maybe its knackered!
I am useless on this type of thing, but may be able to help a little with what I have seen people use.
I think what you have is called a hunting crop (a hunting whip is the one with the long dangly bit). I am not sure whether you should carry one in the ring unless you are associated with a hunt. Anyway - you rarely see anyone carrying them in the "normal" class, although some people will carry them in a championship if they are wearing full hunting gear. I wouldn't jump with one as you are likely to cause yourself an injury! I would also not use it in an in hand class.
I am sure Virtual will have a better idea than me on this as she is well into her hunting!