I had occasion to merge two user accounts for the first time today. I was unsure which account to hit the button on but took a chance on the account-to-be-subsumed.
Fortunately the dialog to choose the target account made it clear that the account I was acting on was the one that would disappear.
And then I got a confirmation dialog where I had to type in transfer @account-to-be-subsumed to @survivor-account which gave me plenty of time & opportunity to double-check and make sure I was going in the right direction.
I really appreciate the thoughtfulness of this workflow. Thank you.