Rewards decrease from 23% to 15% . OMG 
No, they didn't. 23% were for both ACT and BTT. Now the signature bounty was separeted and each forum has own 15%. So they are not decreased, because number of participants is less on each forum. 
I can also confirm this as read it on bct, before it was roughly 11.5%, as the sig campaign was pretty equally split between bct and act, now both platforms get 15%. That's roughly a 4.5% increase from current active participants, which improves the value of this signature bounty considerably.