What "type" is indeed the point here. I almost missed it without the Holy Ghost hinting at that. I thought it was literal but kept coming back at the type of sign. I assumed it was positive sign but it's not. If an unbeliever walks in on people talking in "tongues" at a church, that's a guarantee its a sign for an unbeliever alright. It's a sign that they were right its not for them and will walk out. This sign is a negative one, not like a positive one for a believer (and even so its better to pray alone with tongues for your own belief and edification, and if lead in public, to have an interpreter). But later you see that prophesying is different and that it cuts deep at the heart. So this would be a "negative" sign for the unbeliever, if you will, at the moment, unless they become a "believer" by repenting and turning to the true Most High living God.
