Sorry to bump this, but I'm coming back at this.While importing users if duplicate users are found, they can either be automatically merged based on email and username or you can choose which action to take for each.
I just converted my own forum via the importer. So from IPB 4.4.10 to Xenforo 2.2 and I got a warning that there should not be any existing users. Thinking of your answer I ignored this warning.
Now this happened:
Username conflicts Black Tiger username changed to Black Tiger1 Email conflicts Black Tiger1: Email changed to email@example.com
But I thought you said the names would be merged. I did not get a choice which action to take.
Both usernames were merged, but not into the already existing account Black Tiger. The new account Black Tiger1 was created for this.
Which is not what you said in post #7.
This could cause huge issues when importing the SMF forum which has some users which exists on both forums. So I would really like to know how to solve this.