A forum with 26596 users is NOT the place for a birthday thread for a single person. I am also in other forums. The one of my alliance (8 members, another RPG) is quite small and very personal (we know each other and meet each other outside the forum). We have a single birthday thread in there which gets new posts when there is one. Nobody has problems with feeling unimportant because we don't open a new thread.
I am well aware that a lot of persons in this forum are also friends (It doesn't really matter if you see each other in RL) and want to send gratulations, BUT if you are friends, then you might also have different means of communication (messenger, phone, a dove, ..., IGM) to send some greetings. The only reason to make a public thread is to remind others of the event, but since there already IS an automatic reminder and this is NOT a small community forum this is not really helpful.
Everything in its right place.
Birthday greeting threads are as appropriate in this forum as me selling a bike. Yes, I don't like a lot of other threads in "Hydlaa Plaza" as well, but this kind gets so redundant.. There are also appropriate threads, too. I think there are some good threads to get to know other players.