Powerful figures of the War Seas get personal titles of their own, like Commodore Kai, who’s called the Red Sabre. So, why can’t we get one later on?
Unlike the other “Personal Traits” (like cooking, brewing, jewelcrafting, dodge reflex, etc), this one affects the Juraserva and the story. The Agora will refer to you as “[TITLE] [NAME]” just like with the pre-existing titles. Of course, this doesn’t stop you from flexing that you explored the Epicenter because even after you get your own personal title, you can still used the ones you achieved through doing something amazing. Other than the Agora, later on in the story, some story-related characters will refer to you by the personal title due to your reputation. In short, this is merely meant for immersive purposes (and it’s pretty cool imo).
You’ll only get your personal title after you kill the 3rd High Lord, because by then, you made it known that you’re extremely powerful and you deserve a personal title. Now, for my take on how you get it, if you (in disguise) return to the capital island of the sea where you killed the High Lord, you’ll get the option of talking to a new Juraserva journalist who’s panicking over something. Walking over to them and asking them what’s wrong, and they’ll tell you they’re responsible for making an article about you, not knowing the person they’re talking to is you in disguise. The journalist wants to give you a personal title to ‘give the masses something to talk about’, and if you say you’ll help out, that’s when you can choose your title. Like strong NPCs’ titles, it’s directly based on your arsenal and trait, with the first part of the title being an adjective or a color, and the second part of the title being a noun. You can change your personal title at any time you want, as it’ll be in the info bar.