Sounds like this bug is not something that affects everybody. If you have it I suggest working with support and building a dialogue with them, sending them test cases, etc.
When I try to add someone to FL, I get "Friend request already sent", and there is no purge the status. Unfortunately, the support in this matter hasn't been all knowing about the problem, so for some people it's pretty stuck.
When it's bad is if you're coordinating an event, and you need to see at a Point in time if certain key people are online or not, and you need to be able to Contact them swiftly (without having to to through player register and copy & paste link from there). If you need to Contact one and you have plenty of time, sure, but it's stressful if you're at a stage when you have 5 minutes to coordinate maybe 20 people.
The problem is fairly easy: You try to add someone to FL and they're not reachable (ie offline). Then the friend request goes into limbo - when they log on, they don't see the friend request but it still exists (in limbo). Hence, you can't send a new friend request (because there is one already - in limbo) - even when they are online.
This was a problem at least up to two weeks ago.
Also messages like items expiring from banks didn't arrive when you've been offline (so if you don't visit the bank regularily to check, you might find that some of your bank loan deeds mysteriously has vanished, and the only clue is looking in auction (as the bank manager doesn't know what items belongs to whom as items expire). I've lost items this way. Some items I can buy back, but the bank manager sold a batch of (White) paint Before I noticed the bank loans deeds were gone, and that I will "never" get back.
Also, it seems you only get supply response notifications if you are online.
Maybe it's been silently fixed.