Regarding salt, "the experts" don't seem so confident on what levels. In the past few years, the daily recommended intake of sodium has increased.
If you are burning 5000 calories a day hunting or farming, eat all the sugar and fat you want (and can get by your own efforts). But if you are burning 2000 calories a day sitting at a desk... You can't debate food in a vacuum without considering lifestyle.
If one does not believe that they were trolling (i.e. they do not believe that they were doing what trolling is. This is a belief about what they were doing, not a belief about what the word "trolling" means), then that seems like fairly good evidence that they were not trolling.
I don't know what would be a better (and available) measure of one's intent than one's own perception of one's own intent. (Of course, one could imagine that there might be a better source, but in practice I think it is the best evidence we have).
This would only be as convincing to oneself I suppose, but I think that one's memory of one's intent is generally fairly good evidence to present to oneself to show that one was not trolling.