I was messaged by and responded to both. I suspect they're different people.
I also am not sure they're scams in the traditional sense. An employer match is the sort of thing that encourages this sort of thinking:
Whether or not this is within the letter of a match policy depends on the specific policy, but it's typically against the spirit and recommended against by Double the Donation. So even if there is no lurking chargeback, I would caution against this as burning the commons for short-term gain.
Also, if you have a strange story, keep Robin Hanson's recent Facebook post in mind:
If someone ever wants to give me $1M+ out of the blue, I hope they'll do more than send me an email w/o phone number I could call to confirm
Keeping that in mind, so far hans_jonsson seems legit. (I've only put a moderate amount of effort into verifying his claims.)
I was messaged by and responded to both. I suspect they're different people.
Update: they are different people, but the first one was working for the second one.
Recently, multiple suspicious user accounts were created on Less Wrong. These accounts don't post any content in the forum. Instead, they are used only to send private messages to the existing users.
Many users have received a copy of the same message, but different variants exist, too. Here are the examples I know about. If you have received a different variant, please post it in a comment below this article:
I don't know yet about anyone who replied and got scammed, so this is all based on indirect evidence. If you got scammed, please tell me. If you are ashamed, I can publish your story anonymously. Your story could help other potential victims.
Most likely, the scheme is the following:
(Thanks to ChristianKl for explaining the system in the Open Thread.)
If you replied to the original message and now you are already in the middle of the process, please inform your bank as soon as possible! Even if the step 2 didn't happen yet, so you can still get out without losing money, warning your bank about the scammer could help other potential victims.
Warning: If you have already received a check or a payment confirmation, and someone is asking you to send the overpayment back quickly, do not send anything. The check or the payment confirmation is fake, and the goal is to make you send money before you find out. (Thanks to qsz for explaining.)