If you want to look for verses about how to carry on a discussion, proverb books are probably your dealie.
For example, Sirach 5:11-14:
“Winnow not in every wind and do not start off in every direction. Be consistent in your thoughts, steadfast in your words. Be swift to hear but slow to answer. If you have the knowledge, answer your neighbor; if not, put your hand over your mouth.”
Also, we have the famous introduction to 2 Maccabees, which explains that it’s darned hard work to edit and abridge a book so that it will be useful for all.
However, other than discussions about fools multiplying words and people avoiding uncomfy topics of their own sin, there’s not a lot of talk about staying on-topic. Jewish people like long discussions that range widely, and Jesus’ preaching doesn’t seem to have been much different.