Dear A:

You wrote:

a. He talked to Jeff, angrily.

b. He threw the ball, with all his force.

Normally, the commas in these sentences would be considered superfluous. However, I think they might fulfill two functions: 1. They might indicate that what follows them is an afterthought. In this case they would be reflecting a pause in speech. 2. They might make the second part becomes parenthetical and increase the weight of the first part. The second part becomes parenthetical/ What did he do? He talked to Jeff, and (what’s more) he did it angrily. He threw the ball, and (what’s more) he did it with all his force.

Would you say that analysis is correct?

I understand what you are saying, and some people do use commas that way. However, it tends to be confusing because commas usually mean something else. If you want to show the afterthought, use a dash. That is the main reason we use dashes—as an afterthought or for emphasis. That way, too, there is no ambiguity about what you are trying to say.