Alright, but I am not a fan. Don't like it when a device tries to be smarter than me...
actually, it is a bit more funky than that. I entered the SIP number for a Skype contact and I appeared in the contact profile as a toolbar, but then later disappeared?!. I have open IM conversation with these contacts and on top it displays the number and when I press the contact icon next to it is opens the correct contact card but there is only the skype toolbar there. So I tried to go the unmerge view as you suggested but there is only the skype there also. Contacts with just SIP are ok, the SIP toolbar does not disappear and the number is visible when I go to unmerge.
I use a local sim (finnish) card and the SIP I mainly use is provided (I pay for) by the mobile provider from another country. Through this SIP account I can call and send SMS as if I were in on the other network and it displays my non-finnish number to the recipient. If I try to send a SMS, I cannot add a SIP contact as recipient.