I managed to find a few hours over this weekend to code stuff
The GDU experience and leveling system is live. You will get a certain amount of experience for basically every action on GDR. Posts are obviously worth the most experience, followed by making comments. Receiving likes and followers will also get you a decent amount.
If you head over to GDR now, you'll get a pop-up saying that you've leveled up. I ran a script to calculate everyone's experience to date, so the system is starting as if it was live from the start. You'll get a pop notifying you each time you level up :D
It uses an exponential type function. I've copied an algorithm I found on game dev stack exchange. At first, you'll really jump in levels, but it will start to slow down. The goal is to encourage people early on, but ensuring the regulars don't appear miles ahead (coz the exponential function requires more experience to get further levels).
Your level is now integrated basically everywhere your avvy pops up (featuring the resident ghost, because he's currently leading GDR):