It all comes down to famepoints, your rank, and level.
It is a lot of calculating, but to keep it simple: the more famepoints you have, the higher your attacked targets must be. The higher your(or your foe's) rank is, the easier it is for higher level characters to start a duel with a lower level player. That's why we luuuurve those god-modies.;)

Another reason why you might not see a arrow is because that person is a lower level than you and you can't attack a lower level character..... Have fun in the world of Larkinor

Andi;)