1. A method for automated comparison of Darwin Information Typing Architecture (DITA) documents for revision mark-up, the method comprising: reading via a processing unit document data from a first DITA document into a first document object model tree comprising a plurality of nodes, and from a second DITA document into a second document object model tree comprising a plurality of nodes; identifying and collapsing via the processing unit emphasis subtree nodes in the first document object model tree into their parent nodes in the first document object model tree, and emphasis subtree nodes in the second document object model tree into their parent nodes in the second document object model tree, the collapsing comprising caching emphasis data from the identified subtree nodes; the processing unit transforming via a preorder traversal the first document object model tree into a first pre-order node list, and the second document object model tree into a second pre-order node list, the listed nodes each comprising primary sort key information and document structure metadata, and wherein the transforming captures adjacent sibling emphasis subtree nodes as single text nodes; merging via the processing unit the first and second node lists into a merged node list via a first phase longest common subsequence process that recognizes matches of node pairs from each list that have primary sort key information and document structure metadata meeting a threshold percentage of match, and that saves differences between matching tokens of the node pairs; refining table comparisons in the merged node list via at least one additional longest common subsequence process; building a merged document object model from the merged node list and the refined table comparisons; and transforming the built merged document object model into a hypertext mark-up language document that displays the saved differences between the matching tokens as word-level highlighting mark-ups within the refined table comparisons.