If the gift of tongues or xenoglossia has been a sign in times past of judgment by God, it makes you wonder then, regarding sign of judgment, what judgment it tells of now because it does indeed happen today. God is wise in ways we cannot fully understand. He was wise when His Son whom He loved was put by His will up on a cross of wood to cure the believers of the effects of sin and guilt of sin and power of sin but can we fathom that wisdom? No. It seems foolish. Yet love for us prompted it in God. Why a cross? Why such a cure? Why the similar snake on a pole in the desert with Moses? Why Jacob setting up poles with stripes in by his sheep where they drank and so increasing his share of sheep with stripes? All weird and wonderful but wisdom from God. So too is tongues weird and wonderful and wisdom unfathomable. A sign yes but a sign that God will have us speak even to those who cannot believe. "Mene mene teckel upharsim" If judgment has started with Israel and with the house of God what then will it be when it comes to all the world. "Weighed in the balance and found wanting" For unbelievers it is a sign their unbelief is sin. We need to think about the judgment implicit in tongues. It warns us that God could harden us and others as an extreme punishment. If He speaks incomprehensibly we would get hardened in our hearts unless He gave interpretation, like Moses' Pharaoh was herdened by God as a deliberate act of wrath by God. We would end up ever hearing but never understanding and would harden our own hearts against God. This gift is like a message at gunpoint. You have reminded of this. If God withdraws it with a people and speaks clearly or if He always includes interpretation it is like Him putting away the wrath and only showing the mercy. But the wrath is still there as a reminder to listen while we can.
