Basically you select an icon and it pins it over the head of whoever you're currently targeting.
I assume it's mainly for organised groups doing trials and things. My other MMO has a similar system where the group leader can put markers either on the ground or on people or NPCs and they'll use it to indicate things like someone in the group to follow if you want a bonus objective or enemies to watch out for besides the main boss. Or just to indicate roles beyond the basic tank/healer/DD.
As far as I can tell if you're not in a group only you can see it, and I can't think of any situations where I might want to mark something for myself.
PC EU player | She/her/hers | PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!
"Remember in this game we call life that no one said it's fair"
It is something that desperately needs a toggle so we can opt out of seeing them. If it is working as intended it really needs the ability to opt out. Last night while doing a world boss someone (I am assuming) put an icon on a little spider. One of those spiders that you one shot for bait. The icon was over the spider and on the compass bar. Was a distraction and the little spider was right where it wasn't real convenient during the fight to go pop him.
If the icon wasn't placed there by another player then the system is bugged and needs fixed. Either way I don't want to see them especially on the compass bar. A player in a trial group was putting them on other members (again assuming) and for me at least was nothing but an annoyance.
and then the parrot said, "must be the water mines green too."