If you're really going to leave, leave. Don't say anything.
Honestly, I doubt anyone is going to miss you.
This is just an attempt to make yourself feel like you made an impact on anyone or anything here.
Your friends will forget you in a week, memories fade and friendships do too. And considering these being made over the internet, that only speeds the process.
And like I always say, you'll look stupid for coming back after making this thread, if you do come back.
I may sound like an asshole, but most likely, I am right.