Oh man. When someone insults you, place yourself above them with your retort. Also, don't turn your own argument into a straw man by making assertions that are clearly false, such as that they confuse you with Harry Potter. They don't actually think you're Harry Potter, they know for a fact you are not and make fun of you for it.
You kind of just have to take a lot of those hits. Especially the one about you conjuring a new bike, since that was actually clever and funny you're kind of forgeted by that one. You also really can't argue that you're not gay because that's so cliche that it'll just provide fodder for them to make fun of you with.
The best one to argue against is that you're Harry Potter. I personally would do this by figuratively catching the punches. For example, posting something like "Broomstick got old, guys. Upgraded to this beast." It's literally no fun to make fun of someone for something that they're willing to accept. It also diffuses the rest of the things they can say about it. Like, this would never happen:
"Hey Harry Potter, where's your broom at?"
"Left it at home today, sorry!"
"Pfff... Harry Potter nerd!!!!"
At that point they just sound stupid. So you can just laugh it off and ignore them, you literally don't need to say anything. The second thing it does is it puts you in a position to make a jab back. Like so:
"Hey Harry Potter, where's your broom at?"
"Left it at home today, sorry. Sounds like you did the same with your sense of humor."
Boom. Owned. You don't even have to say anything that clever, as long as it doesn't sound stupid it's a KO. There's literally nothing they can say to insult you back without sounding stupid unless it's REALLY clever.
You've also got it easy because it's on the internet. You literally have a ton of time to hand craft your replies to be clever, funny, and sharp. In real life you can't stop and think of a retort.
