You might have wanted to say that no one can agree on what speech is trolling and what speech isn't, but that's not because the word is vague. It's because people disagree on the deliberate and the upset part.
There may be a good moral argument to draw that line differently when the consequence is a ban from a commercial platform vs being locked in a prison.
No definition is as concrete, unmallable, and unchanging as you seem to imagine.
Truthfully, the two observations are related: The word "trolling" being kind of vague is probably the main reason why people do not agree on what actually constitutes it.
what then, in your mind, is the clear, precise definition of spam?
I am kind of surprised at how many different ways people have interpreted what I said. I'm frankly feeling a little defeated.
How is that not trolling?
Argueing that something is trolling because it solicits a reaction, or that because it's disruptive it counts as trolling, doesn't make sense. You can't distinguish trolling without knowing someone's motivations. Posts that could be trolling could just as easily be venting, or bringing up a genuine concern that just happens to be contentious, or etc.
Otherwise, flaming people in general is obviously trolling. That's not the way the word trolling has been used historically.