Basically glyph of Falling Meteor gives you a buff of Meteor Slam, which makes you unable to go below 1hp no matter how much dmg you would be recieving. However if you jump to places that would otherwise kill you i.e. Eye of the Storm depths in the middle, you just slam down there while still being alive with 1hp. Once you reach the bottom in there you can move freely, but you will be stuck since there is no way of getting out. You cant even kill yourself with Hellfire, it only ticks your hp down to 1. There are other "bottomless pits" like Lich King platform, but in those you stay in movement and cannot thus control your character. Also LK doesnt follow you down so no use there... Basically you become immortal with this.
However, if you enter the EotS while on a FLYING mount, you keep the "Meteor Slam" buff after EotS ends. You will become immortal as long as you dont touch the ground. Nothing seems to be bringing you below 1 health. Tested against npcs & players & fatigue. You can still get dazed that knocks you off your mount so be careful of that. You will lose duels since it only requires to drop to 1hp.
Also you keep the Meteor Slam visualization on you.