Long time no post
I would look at this issue from what I would consider a more practical standpoint, perhaps.
If President Obama were to appear at my door, and speak to me, I would recognize him as such. Even if his voice were off, due to sickness for example, it would have some "tell-tale" signs to it I imagine. I have heard it enough times now via the media, that I'm guessing I could recognize it as his, especially so if we were face to face. Now, could the person in front of me be a look-alike ? Yeah maybe. A celebrity impersonator perhaps ? Perhaps. But there would be other factors that may help me to decide, "Yup, this is really the POTUS at my door." The presence of Secret Service, perhaps other media, etc ... all factors used for me to help determine if this is really, in fact, Obama. Do we live in a day and age where someone's physical appearance can be altered to such a degree that I may not be able to distinguish an impersonator from the "real deal" ? We may finally have reached that point, depending on the person being impersonated. But still. There is a good chance, I would recognize and correctly identify the POTUS. Unless he was intentionally trying to alter or hide his appearance and voice.
Now, if I got a phone call from the POTUS ... that is a different situation. Without any face to face, and only a voice ... how do I know it's really him ? Voice impersonations can be mimicked extremely well. What if it's simply someone whose good with voices ? A comedian for that matter ? In order to know that the voice on the other end of the line were really his voice, I would most likely need him to verify it separately, to endorse what was said, to verify what was said, etc. To clarify. Similarly, if I saw something online or written on paper, that was claiming to be attributed to President Obama ... how would I know he really wrote it ? Getting him to clarify, would be important. Otherwise, I could attribute something to him falsely, that he never said nor endorsed. Or, if I was confident it was him, either in letter or over the phone (for example), I could go ahead and assume I suppose. But in order to have that confidence, I would most likely need to really know him, on a personal level. Not study him and watch him on TV, but interact with him, on a personal level. Get to know him personally. Not as an observer, but as a participant with him personally. And after having built that experience and time with him, I may be able to know his nuances and mannerisms to such a degree, that simply by hearing his voice over the phone, I could perhaps tell correctly if it was really him, or if it was an imposter. Consider a close relative or family member, or best friend, someone you are really close with ... you can recognize them and correctly identify them in written word quite often, over the phone, from a quick glance. Why ? Because you know them, intimately ... your familiarity with them is personal.
But that familiarity takes time, and experience. Without that ... how could you even say with confidence, if such a person were standing before you, that you could even correctly identify them ? Even if they were famous for that matter and a well known celebrity ?
The issue of identifying, therefore, someone standing before you, verses a voice over a phone, or something written down ... are wildly different.
There are accounts, all throughout history, of individuals claiming to speak with supernatural or spiritual entities and beings (i.e., this would include "God"). Whether we are dealing with modern major world religions with millions of adherents who believe they are correct, or ancient polytheistic accounts we mostly now recognize as "myth". Whether we are dealing with someone who believes they can channel dead relatives and psychically interact with extraterrestrials from other parts of the universe, or they believe they are hearing God tell them how to win a football game against another team that is also praying for a win ... an issue which is often over looked, I think, is of *identification*. Because suppose you could verify, with evidence, that a person was communicating with an entity of some sort that the average person would consider spiritual/supernatural/etc (i.e. God would fall into this category) ... how would you positively identify the speaker ? And if the speaker identified his/her/itself, how would you know it wasn't a false identification ? An imposter ?
In the scriptures, there are accounts which suggest that people interacted with a physical being they identified as God/Yahweh/etc. Not only in the Garden, but outside the Garden accounts (Abraham, etc). So let's say a physical being appeared at your door, and said, "I am God." What would it take for you to positively identify this being as "God" ? Miraculous and powerful acts performed ? Would this being need to prove their identity by referencing scriptures to you that you interpret a certain way ? If they referenced 99 scriptures in agreement with the way you interpret them, but claimed that 1 scripture you interpret to mean one thing actually means another or was even a mistake ... would you no longer identify them as God based on that one issue ?
Moving down the chain of communication ... let's say you had no physical being appear at your door, rather, you had a voice start talking to you in your mind, and your body started having certain types of feelings as a response to the voice. What would it take for you to identify the voice as "God" and not just your own thoughts and feelings ? Now, let's say you heard the voice outside your mind, with your physical ears, audibly ... but still no physical entity appeared before you. How would you know it was "God" and make the positive ID ?
For those who believe they could identify said voice/being/etc as "God" based solely on their interpretation of certain scriptures ... even if said voice/being/etc were to perfectly affirm every belief you currently hold and seem to be in agreement with every interpretation you currently hold to be "God's truth" ... how do you know it's not some other entity being a really good impersonator ? How do you know it's not Satan, demons, angels, aliens from another galaxy, a ghost, etc ... and they are saying exactly what you want to hear, to convince you they are God so you'll positively ID them as such ?
See ... if Obama were to appear before us, in general, we would probably not question that it were really him. A conspiracy theorist may go the route of "he's an imposter, a reptillian shapeshifter, a clone," etc ... but those people are more likely to be looked at with scorn or skepticism, than accepted. A letter claiming to be penned by Obama, or a phone call claiming to be Obama, would be met with more general skepticism perhaps, depending on the content. But again, it could be clarified by simply asking Obama himself, and getting him "on the record".
So all of that to say, practically speaking ... to make a positive ID on "God spoke to me" ... be it through an audible voice, a manifestation, a thought in your head, a feeling you get, inspiration you feel when reading a text you hold to be endorsed by God/inspired by God/written by God/etc ... to make that positive ID, you would ultimately need to get clarification somehow. You would need to get "God on the record". Lots of people claim to hear God, and quite often those people do not agree with each other that they did in fact hear God. One will say they did, another will say they did not. Lots of people try to use holy texts in order to make the positive ID, but people disagree on what the holy texts imply, and which texts are even to be considered as proper measuring tools for that matter.
So, practically speaking, how does one make a positive ID on God in an "I interacted with God" scenario ? Whether you're claiming to have heard God, seen God, or even claim you know what God meant by something God is claimed to have said ? To me, the OP issue goes beyond those who claim to hear God audibly or any other type of experience along those lines ... it cuts right to something even more foundational: how do you even know God said this or that in the Bible ?