Understanding one another in the Fellowship

[Eressië Ailin]

When they were all at the gate of Moria you will notice that the words were written in Elvish, Quenya I think, and Gimli certainly knew what it said,

Gimli may have known what it said, but I don't think that he could read it. Gimli seemed to know quite a bit about (ancient) Moria, and was quite eager to go there. Many of his relatives could have simply told him what was written on the Gates of Moria. He didn't have to be able to read it.