there's no way to know if someone's faking it really, and we all know that people do all kinds of things to posture their religiosity. it says that in the bible. i suppose that if someone heard the message interpreted, and it really meant something to them personally, and it was impactive to them, i could see why they would have a reason to think it was legit.
i've thought about this a lot because like i said, my grandma used to speak in tongues, and i've been really close to her all my life. i'm also a person who's had all kinds of weird spiritual things happen to me, but have never been even remotely inclined to speak that way, or have i had any impactive messages delivered to me that way.
my grandma was an honest, decent woman as far as people go. i KNOW she loved jesus, and was very sincere in her faith. i never got the impression she was faking it. i was knee-height into grade school when i used to go to church with her, and i'll tell you my honest impression from back then and now.
first of all, she used to do it a lot when i was very young, and while they attended a small and hometown church of god. i hated it. it scared me, and i wished she wouldn't do it. though it was somewhat fascinating at the same time. i just didn't like the attention probably. i was a shy kid. i didn't like that church actually. the people were fucking crazy; everybody all crying and laying hands and falling down and running around in the aisles. to me, as a child, it was like romper room for adults, and it was creepy. they used to turn that shit on and off, as if it had a switch every sunday. she used to have prayer meetings at her house too and it was the same thing.
it was like play time with god, or play time with the spirit. it seemed that way to me then and it still does. like they were playing with it as if it was a toy. they were genuinely intrigued by it obviously, and they may have had reasons for coming together like, if someone was sick or whatever. but really i got the impression that it was just a fun, exciting thing for them to do.
and then, at some point they left that church and started attending a much larger church that was not in their hometown. the congregation was quieter (which i appreciated), and grandma didn't speak out nearly as much in that church. and over time that church built a much larger new church, that attracted a huge congregation, and the speaking in tongues ceased entirely.
i don't necessarily think the spirit doesn't have a language, and that there may be times when being gifted with it was purposeful. i just don't get the impression that within religiosity, that is what's going on. i think it's purpose is more of cultural, recreational, or ritualistic perhaps.