In the context of applications such as finding messages dealing with a particular topic, or finding inter-conversation topic groupings via centroid-based clustering methods, the essential text of a first message is adjusted to avoid vector distance distortions based on differences in quoting styles. Text is deleted from the first message if that text constitutes an entire prefixed or suffixed second message (typically a parent message), while selective quotes in the first message are included in the adjusted message because these are considered to form a logical pan of the message. When the first text does not contain any quoting portions of the second text, an analysis is done to determine whether all or part of a second text constitutes a logical reference to the first message. If so, all or some parts of the essential text of the second (parent) message are included in the adjusted message.