From an actual published article in a major magazine:
"After clashing with S over his partisan journalistic agenda, G quit months later."
Okay, tell me WHOSE partisan agenda? S's or G's?
In fact, when the readers read quickly, they might get whatever meaning makes sense to them, whatever fits the pre-existing opinion created by the previous paragraphs, maybe. For example, I assumed that G quit, so probably S had the agenda. But maybe his boss S had rebuked G for G's agenda, and G quit in order to avoid being fired. That's just as plausible.
The reader is confused, and it's the writer's fault. When there are two people in the sentence who could be the pronoun, the writer simply has to find a way to make clear which. You have to be ruthless to root these out. They're perfectly grammatical sentences that make sense on the surface. But because there are two alternate interpretations, and both make sense, the readers will have to work to figure out which you mean.
Yes, the reader might occasionally benefit from working to understand. But make that because the concept or process of thought is complex, not because your writing is bad. Save the sentence ambiguity for ambiguous thoughts.