Speaking in tongues is only an indicator that an otherwise decent human being believes in their own imagined fairy tale.
It's supposed to be more than just that. Speaking in languages one never learned made it possible for the uneducated disciples to preach to people who would otherwise not understand what they said. What you hear in Pentecostal churches is something different because those tongues they speak aren't real languages.
This sounds like ducks tails. I was taught this as a young child growing up but we can't prove that it is real or not.
I actually haven't experienced this or even witnessed this happening. With regards to some people speaking in tongues that are similar with each other, we cannot really assume whether that is because they heard it before or they are really baptised by the Holy Spirit. So for me, as a Catholic, I cannot doubt or not doubt that this can really happen. But so far, I haven't experienced this. I do believe in my religion and all that, but it's hard to say that this is true when other people do not believe so. I think that it is a matter of your beliefs and religion if you will believe these things.
Well, if wikipedia says so then it is the truth. I don't know really. Maybe it happened once that someone was actually speaking or addressing from some other side but also it might be the wikipedia explanation in some cases. Who would know these things. We cannot know everything, quite contrary, we know very little and accept even less.
I believe the ability to speak and be heard by any despite language difference is in fact proof of the Holy Spirit. In my mind, this is not gibberish that everyone can understand, but the words being spoken through all of the different languages at once, and the people of different tongues just hear it in their language. As this is not humanly possible, I do believe it is proof that they are Holy Spirit filled.