It gets rather annoying and frustrating getting constant party invites while in a run or trade requests, friend requests, and guild invites from people whom you do not know and on top of that they never even said "Hi" to you. An option to disable invites individually would be quite nice.
Also, it doesn't make sense that you can receive guild invites even though you are already in a guild.
I'd rather just have a more subtle notification window. (the one that covers your whole screen just to say "noob wants to trade with you" or "helpme has invited you to join them in an impossible dungeon" is very frustrating) Maybe have a side tab that looks like the events bar that holds all your notifications, and you can minimize it if necissary, and it doesn't prevent you from speaking?