The novelty will wear off soon enough. There's nothing wrong with players showing off a well earned mount, but to be annoying with it, is disruption of game play. There is no excuse for sitting at an NPC that you can't interact with while mounted, other than to be annoying with it. I don't like to be even partially buried by another players mount for a period of time. It doesn't matter if I can still see the NPC or not. It's obvious they are trying to annoy more than show off their mount. Be respectful and dismount before you walk up to any NPC to interact.