I feel as though the multiple coin types is a bit silly. Just have one coin type and apply different multipliers based on activity/donations/whatever. As a generic example: Activity is worth 1x coins, donation is worth 1.5x coins, and whatever activity is required for Activity2.0 coins is worth 2x coins. (Substitute the multipliers that make sense.) The current system is needlessly complicated and has to be much worse to maintain, not to mention confusing for users.
Also, just generally speaking, locking content behind paywalls is a huge put off to users like me. I've been here almost 4 years now, but I rarely post. I'm just not a social person like that. I look for information, find it, and move to my next task. I am also poor thanks to taking a massive pay loss after being laid off, so I can't even afford to donate anymore, though I have in the past. I'm lucky in that Members+ is already unlocked for me, but my time and cash is limited, and as such, I can't justify spending money on unlocking something unless I know exactly what I'm getting in return. That's not to say I won't donate whenever I can without any perks, just that if there are perks, there needs to be much more insight into what exactly you get, with examples and such.
Which leads to my next question: Wtf is the gray zone? lol
EDIT: Small suggestion for a change in the Shop. Have it display you balances at the top of the page at all times that way when you're clicking around the shop you always have your balances right there in front of you.