There's always going to be, subjectively, a lot of overlap between those two categories in looking at the comments of others.
I know I'm not a troll, so obviously if someone downvotes me it's because they disagree and therefore unfair. But maybe not from their perspective.
You can also downvote and reply; I don't know how common that is. But given the number of people who say they don't know why they are downvoted, it seems to me like a reasonable thing to do.
Yes. "Look at this cool thing MS/Google is doing!" and "Look at this evil thing MS/Google is doing!" can both be seen as trolly agenda comments and relevant ones, depending on where you stand.
I know I'm not a troll, so obviously if someone downvotes me it's because they disagree and therefore unfair. But maybe not from their perspective.
You can also downvote and reply; I don't know how common that is. But given the number of people who say they don't know why they are downvoted, it seems to me like a reasonable thing to do.