Characterizing and comparing the heterogeneity of ordinal responses from survey Let us consider the following setting:

*

*We have two groups Q1 and Q2 of questions

*Several participants answer all questions using a single ordinal scale A, B, C or D for all questions.

Then, I want to test whether answers from questions coming from group Q1 are more heterogeneous than those from questions from group Q2.
What are the available statistics to quantify "heterogeneity"/"homogeneity" on such an ordinal scale ?

Nice question.  The simple “% choosing the most commonly chosen option” should be considered. You could compare the literature on straightlining.
Following @BigBendRegion and Nick Cox’s helpful comments you would treat a set of responses of all As and Ds (exemplifying the “extreme” response style) as more variable than a set with equal numbers for all 4 choices. Will this be tenable? You will want to think through how you can best define variability before committing to ways of calculating it. You probably will want to employ and report the results of multiple methods.
