For starters, people crowding an NPC is easy to deal with. Just hold down your target filter button (I think the default on keyboard is X).
You'll click right through people and onto the NPC or other target, unless you've changed your filter to act differently.

However this isn't a case to make conversations applicable while mounting. No, I just wanted to help people in crowded areas. Speaking to people while mounted is incredibly rude. How you wish to play out your characters personality is one thing, but within the context of the rest of the world, you're mild mannered and polite. Let's not forget this!