When it came down to it, people loved to call Lord Voldemort “Riddle” just because it was a name he did not like and Harry Potter doing it to him is honestly a huge mood.
Harry Potter is squaring off against Voldemort, they’re going head to head and then, in a twist of his life, Harry calls him “Riddle”. So why? For many, it was always Dumbledore who refused to call Lord Voldemort by his fake name.
Yes, his fake name. Because Tom Riddle hated his muggle name not because of anything other than his own prejudices. So Harry using the same tactic that Dumbledore did to change the way that Voldemort viewed himself was more about tearing him down emotionally than anything else.
Why it’s a “mood” is because Harry just said “nope, sorry Tom Riddle, I’m not calling you a lord when you’re not one”. That’s the thing, when you stop and think about it, Voldemort chose to give himself a lordship. No one named him a lord, he just rearranged the letters in his name and realized you could spell lord and went with it.
So yeah, if I was Dumbledore or Harry I would also not call someone a lord who did nothing but murder people and didn’t even really have the title. Especially if he was Voldemort. So Tom Marvolo Riddle is called “Riddle” because Harry knew that it would disarm him and get Voldemort down to his level when he needed to defeat him most. Call him Riddle all you want, Harry.