User blog comment:JmLyan/CC4: Xasus, the Ancient Memory/@comment-24377865-20140703170857

" no cooldown reduction cap, but ability cooldowns will only be reduced by at most 80%."

looks like a cap to me. A cap at 80%.

Also, there really isn't a reliable way to stack CDR. Maybe AP ratios, however...

What the guy who makes the CCC series means by "spammable" is like Kassadin ult.