Is it possible to merge two users?

We don't have any user merge extension here and there's no plan to install it, so I'd just decline this request. User:Sveinki has less than 500 edits; User:Sveinn í Felli is older, has an email address and was used recently. If you just stop using "Sveinki", you'll be fine. I can block and/or rename the account you don't want to use and you can place a redirect from one username from the other. We can also recover the password of either account if you lost it and the email address doesn't work.

"you can place a redirect from one username from the other" - yes, that was in my initial request. How can I redirect User:Sveinki to User:Sveinn í Felli ?

I've redirected them for you.