Hah! Jay, the aspirins have kicked in and the headache is mostly gone! So...
First, I aim to draw an analogy between our perception of light and any perception of deity (I will number my points so that it is easier for you to refer to them).
1) Let's begin by distinguishing between "light" and "photons". The two things are sometimes considered identical, but in this context I would like to use the word "light" to mean merely our perception of photons, and "photons" to mean the particle that creates our perception of "light". So, for instance, I might say, "I perceive photons as light."
2) There are in some ways significant differences between photons and light. For instance, light has color -- red, green, blue, etc -- but photons have no color. Again, light does not appear to us as particles. But photons are particles.
3) Now suppose you were to have an experience of "god" (By "god" I mean any deity), and during that experience, god imparted to you some knowledge. Let's say for the sake of discussion that he told you he was "a Tibetan Buddhist".
4) Would you now be able to assert with certainty that god was a Tibetan Buddhist?
5) I think there are several reasons you would not be able to claim certainty. However, I am only concerned here with just one of those reasons. And to explain that reason, I offer the analogy of photons and light.
6) It seems to me possible that there could be as great of a difference between your experience of god as a Tibetan Buddhist and the reality behind that experience as there is between your experience of light and the reality behind your experience of light (namely, photons).
7) In other words, just as light differs from photons, god might differ from X ("X" being the reality behind the perception of god, just as photons are the reality behind the perception of light).
8) Since it's possible for there to be a difference between god and X, it's possible that your knowledge of god as a Tibetan Buddhist is no more knowledge of X than your knowledge of your sweater as yellow is knowledge of some property of a photon.
9) PLEASE NOTE: I am not arguing that the reason or cause of there being some possible difference between god and X is that there is a difference between photons and light. I am only offering photons and light as an analogy of a possible difference.
10) Last, all I aim here is to point out one way in which we cannot be certain that an experience of deity imparts true knowledge of the deity. Of course, I do not aim to suggest that deity either exists or doesn't exist.
I so hope this makes my ideas clearer. And I apologize for any confusion I've been causing.