I mean they are facts in that most everyone agrees on them, which is one usage of the word "fact". But they're not facts in the same way as "the sun will rise tomorrow" or "2 + 2 = 4" (which those statements themselves are two different types of fact also!).
No, facts are facts even if no one can prove it. It's just that if you can't prove it, you can't know if a certain claim (like "the sun rose today") is actually a fact or not.
I think what icebraining was trying to say is:
A fact is not a opinion that is proven to be true.
A fact is a opinion that is true and can be proven to be true even if we don't yet know how. In which case we simply don't yet know that said opinion is a fact.
I'm not sure if this definition is correct but I'm fairly certain this is what icebraining meant.
