So its rather harmless, but i imagine it can create problems.

I was running Interpid; Hammerknell on my lvl 23 cleric, Defiant Highelf, former Eth, Wynja@zaviel.
When we killed Akylios i wanted to leave the group because it moved on to Mind of Madness and so i left, nothing happened i was still in hammerknell.
I took the portal blue portal that spawns when the boss died and reached the entrance, no way out.
I joined the Mind of Madness Adventure to get out, got in there, was in the same adventure group again, did some adventures, left the group and got killed, nothing happened but i died, i was still stuck in the instance, without a group and couldnt respawn.
So i logged out, hoping it would fix it, when i logged in again, i spawned in the Sanctuary of Rebirth, the Tutorial area for guardians.
Everything was hostile or neutral to me, i was stuck in the zone until i portled out with my Tempest Insignia.