Reality check - when I look around at the complaints people have about Bitcoin, merchants constantly being double spent doesn't come up. It isn't "snake oil" to point this out and you should give the people actually using Bitcoin more credit - they know how to avoid losses.

Your double-spending wallet edition is just theoretical - you have to find miners that will take your double spends, and then you have to find users who are willing to accept that most often their attempts to double spend will fail because the bad miners won't find the next block. And then people who use it will discover that if they aren't perfectly anonymous then they will get taken to court for wire fraud, and most likely they will lose.

So there are lots of reasons why people might not do this. And that may explain why this topic is so old and stale. It was being brought up back in 2010 and here we are, years later, people still arguing about this topic and yet there are many more thousands of merchants still accepting these transactions and not losing money.

I remember another topic that used to create endless raging arguments, the 10 minute block interval. Eventually that was solved by Charlie creating Litecoin and now people who hate the 10 minute wait can just go use that instead of creating endless forum threads. I think it's a good way to resolve such disputes - go set up an alt coin that works the way you think it should and then let the market figure it out. Or maybe the Litecoin guys would be willing to incorporate such a change.

Peter Todd Fri, 19 Jun 2015

Yesterday F2Pool, currently the largest pool with 21% of the hashing
power, enabled full replace-by-fee (RBF) support after discussions with
me. This means that transactions that F2Pool has will be replaced if a
conflicting transaction pays a higher fee. There are no requirements for
the replacement transaction to pay addresses that were paid by the
previous transaction.