If you were raised in the church with a biblical pastor, you might have some idea what a “divided tongue” is, but possibly not. My guess is that the most natural understanding is that you have a multiple tongues (of fire), and each one is split into different parts (i.e., “cloven”), but one tongue. But then you get to the second half of the verse and you realize that this fire is going over each person present, possibly 120 people (Acts 1:15).
As you compare the translations, it can get even more confusing. The NRSV says, “Divided tongues, as of fire, appeared among them, and a tongue rested on each of them.” As I said, I am not sure how people would understand “divided tongues.” And then later you have a single tongue over each person.
The problem is that you have two modifiers of “tongues” (γλῶσσαι), both “spreading out” (διαμεριζόμεναι) and “as fire” (ὡσεὶ πυρὸς). How do you say this?
To begin with, the “as if” goes with “fire,” so the NIV places the emphasis on the wrong word. “They saw what seemed to be tongues of fire.” They did not “seem” to be “tongues”; they “seemed” to be “fire.” Granted, the NIV makes sense and what they saw was not really a tongue, so at least this makes sense.