I'm a christian and it would be very hard for me to believe that God posted something on the internet. First of all the when Jesus comes again it would be the end of the world, so I don't think he would leave judging the living and the dead to post on an internet forum. God himself would not post something, but instead have somebody else send out the message. Also, with all the crazy things going on in the world today, and how somebody can completely change who they are on the internet makes it even harder to believe. I mean it could be some lonely old 40 yeard guy named Hank who lives with cats. He didn't take his medication, and now hwe frantically posting messages saying he is God. I mean it sounds crazy but in this type of world it's possible. Just look at the Virginia Tech as an example, or 911. Unless God himself came to me and said that it was he, himself posting those messages I would not believe it. As I said before, when God comes again it will be to destroy the Earth and all evil and take all the righteous along with him.
Peace. Love. Forgiveness.
Blessings and Guidance