It’s getting harder and harder to keep track of how displayed and available titles were obtained. Mist Runner and Mist Treader for example were awarded for WvW Seasons, (if I’m not mistaken) while Mist Walker is obtained in PvP.
A tooltip showing the description of the achievement that awarded the title seems like a simple modification that would add some value to the title system.
This could be displayed in the dropdown of the Hero>Achievements tab, but also when pointing at the title of a targeted player.