As a DecadeClub member, what MegaMegaMonitor enables you to do is to see a piece of DecadeClub “flair” next to other DecadeClub members, anywhere on Reddit. If you’re in certain other private subs (e.g. /r/gildeddrunk, /r/MagicSecrets, /r/The_Haven, /r/MegaEarth, or any MegaLounge) then it’ll highlight your friends from there, too. It’s like RES-tagging everybody from your private subs… but you don’t have to do the hard work of keeping your tag list up to date!
Give it a go! Let me know what you think.
Edit: This is what this post looks like to me, for example, with all the appropriate bits of flair showing.