I asked this in a seperate thread and was referred to here, so I will post it again in case Abustany can explain to me how the fb contacts/local contacts relationship is handled.

In settings there is a very handy option to show facebook availability only to those contacts I have locally. Now I have a contact in facebook, and I want to be able to chat with him. It happens that I also have the same contact locally, but with a different email address so I wouldn't expect the system to know the relationship. I opened the facebook app, found the contact, but the only thing I can do is send him an email. I tried to edit the local contact and add the email address he uses on facebook, but still there is no relationship. Other people suggested switching to full facebook availability, merging the contacts and then deleting the other contacts, but this is too hard work for just one contact.

Thanks for reading. It became too long eventually