This study investigates least delicate patterns of appraisal in two diachronic corpora of UK Parliament
and U.S. Congress speeches over the last two centuries, focusing on diachronic changes and trends of systemic probabilities of
least delicate engagement and attitude polarity. Based on computational algorithms that automatically extract
appraisal instances and intersections from the two corpora, the comparative analysis carried out in this paper
incorporates several statistical methods, including homogeneity or ‘change-point’ tests, Mann-Kendall trend analysis, and
time-series Correspondence Analysis. The results indicate that, in both corpora, probabilities of monoglossic as well as
attitudinal patterns (as opposed to neutral ones) follow statistically significant upward trends. In addition, positive polarity
is increasing steadily, especially in the U.S. Congress. appraisal intersections are also dynamically changing depending
on changes in sociopolitical circumstances. More specifically, in the formative and early years during which party conflicts were
intensified, heteroglossic patterns are favored. In war and post-war periods, monoglossic patterns are more associated with
neutral polarity. In recent decades, during which political polarization hit a peak, monoglossic patterns begin to favor
attitudinal polarity. These findings are discussed in terms of possible causal and correlational interpretations, limitations and
directions for future research.