This morning I've asked a question (on Academia) without registering. I've received an email with a link to set up an account and I've followed it. However it seems this new account is in no way connected with the question I've asked, so I can't comment/upvote/mark as accepted. Have I done anything wrong, or is it supposed to work that way? Is there any way to "merge" the accounts?
It looks like you've asked this question: Is anything wrong with hiring TA as a private tutor?, so this is your unregistered account.
You can use the Contact Us form (the link is in the footer of all pages on Academia Stack Exchange); one of the options in the dropdown is 'I need to merge user profiles.' If you follow the instructions, you'll be able to access the question as if it's your own again.