How often do you get invited to stuff that you deem it necessary to have an entire feature dedicated to declining invites? I can't imagine someone is trying to invite you to a linkshell and after you decline they keep trying for the next hour slowly driving you insane... you decline them once and then you go on with your business until the next awful person tries to reach out and be friendly with you.

For that matter why not just accept? Getting invited to a party when you want to play alone is one thing... but linkshell and free company invites? Even if you're a solo player do you realize the benefits you're missing out on by being THAT antisocial? Beyond just the boosts a FC can provide through actions you're limiting yourself from joining in on group activities outside of purely DF'd content.