Can X Read XChat Messages?

At the technical level, the answer should be no. In a proper end-to-end encrypted design, the decryption keys live only on the communicating devices, not on the server. X's servers relay ciphertext, and without the keys they should not be able to read the content.

But cannot read the content is not the same as cannot see anything. It is important to separate message content from metadata. The content is what you said. The metadata is who talked to whom, when, how often, and for how long. XChat has not yet made strong public commitments about metadata protection, so some of that information may still be visible or retained at the server layer.

There is also an independent-verification problem. Because XChat is not yet fully open-source, outside researchers cannot conclusively test whether the company cannot read your messages claim is implemented exactly as advertised. That is still the main unresolved trust gap.