I've glanced at the Primitive Constitutions of the Order of Friars Preachers before, and I've adopted the view (acquired from fr. Simon Tugwell, OP) that these constitutions represent St. Dominic's major lasting gift to the Church (insofar as they're the means by which his concept of an order of preachers would endure past his death).
There's a lot of interest in the document -- particularly if you're a Dominican, of course. I used substantially the same formula of profession friars were using back in the 1230s (though in my Lay Dominican Chapter we don't prostrate ourselves before asking for God's mercy and the prior's (who is for us a moderator)). Some of it is interesting for antiquarians, and some from the perspective of imagining it were in force today:
XVII -- Scandal If anyone shall have scandalized his brother in any way, he shall lie prostrate at his feet until the one offended is pleased to raise him.
Since reporting faults -- one's own and those of others -- was a big part of community life under the old constitutions, a lot of attention is given to enumerating "lighter," "grave," and "more grave" faults. They range from "To deny or affirm anything with an oath, as some do in speaking" (light), through "To reproach a brother for a past fault for which he has made satisfaction" (grave), and "To strike anyone" (more grave), up to the "most grave fault":
The most grievous fault is the incorrigibility of one who does not fear to admit his guilt, but refuses the penalty.
Such a one was to be kicked out of the Order; not even apostasy carried that penalty.
Though read cold on an August morning, some faults may sound frivolous (e.g., "To sleep during the class lectures"), they all reflect deep wisdom about the discipline that must be preserved and the charity that must be manifested if an order of preachers is to flourish.