I have recently turned my reverse engineering attention to games other than Ultima 1. Thanks to the file format documentation at xu4 and at the Codex of Ultima Wisdom, I managed to extract all the dialogues for Ultima 4 (except for Lord British and Hawkwind, who I believe are special characters). I have added these to a new Ultima 4 Dialogue page, where you can either interactively converse with the NPCs as if you were in the game (e.g. talk to Iolo) or else view their individual transcripts.
These are some known issues: