One thing that stood out for me in the small sample of articles I examined was the flagging of innocuous changes by casual users to correct spelling, grammar, etc. Thus a "nice-to-have" would be a "smoothing" algorithm that ignores inconsequential changes such as spelling corrections, etc. or the reordering of semantically-contained units of text (for example, reordering the line items in a list w/o changing the content of any particular line item, etc., or the reordering of paragraphs and perhaps even sentences.) I think this would cover 90% or more of changes that are immaterial to an article's credibility.