I suggest it's in alphabetic order but when you get a pm that person jumps to the top till you next log off.
Ughhhh I hate pm on pc. We all just need to start walling people when we pm them just in case they are on opc until it's fixed.
@Jester- in the past I used to change my banner and post in wc letting people know I'm on PC so can't see PMs lol. Would ask them to wall me so I knew who it was
Of course, I play on PC more than device, so I hate scrolling down my friends list just to find one or tow pms or even people.