You do know riots get people nowhere right. People have rioted in start for ec snapshot and have gotten in trouble for it, I've heard they've been jailed don't know if it's a rumor or not. Ec should not be refunded, even if 20% or 10% is given back to you. You get what you paid for, if you don't like it, you aren't getting refunds. There's a reason why there's an extra buy button just in case someone accidentally clicks to buy something. They've said no countless times, and I'm sure it will stay that way, this isn't like trade tables.
Speaking of which: those who trade to get tradeable ec items and refund to get ec items they did not deserve. As well as those who who won event items before ec was ever made. And you can't tell them to make it so ec items are no longer tradeable, because those people who traded to get ec items, will have them and will be able to refund them if this happens, when they didn't originally earn them. As well as if you make only those ec items that are tradeable unrefundable, people will complain that they can't refund them. So either way there are problems.
Overall this is a bad idea, and I hope this never happens.