Don't worry about the thread age that much, the Cerberus forum doesn't get that many threads. On the other hand, yes, you pay your monthly fee to Square/Enix, but when you start wasting other people's time, that becomes a problem. You could also argue that the other people could just /pcmd kick such a person, but a lot of people feel like they would be a jerk for doing so. Personally for me to kick someone they need to be doing pretty badly, if possible I'll just add them to my DNP list (Do Not Party with...).
I really do keep such a list, too. So if you're the sort of person who would just behave really badly (attempt to one man "zerg" XP mobs) or something asinine (like trying to ninja lot my Rutter Sabatons, which I still cannot believe happened) or just be a jerk (if I make a vague comment to the party about not trying to one man solo an XP mob, don't call me a princess bard and a whiney ***** and tell me that I'm replaceable, asshat Samurais are dime a dozen), don't expect any sort of in game association with me in game. I just don't really invest any sort of emotional effort into it.
As for thread contribution, don't do any of that stuff >.>;