Negative karma doesn't necessarily indicate a troll, any unpopular opinion can get down-voted to hell while similar but differently expressed ideas get up-voted in the same thread. I'm not against karma system though, just think it's quite useless in most cases.
All comment karma tells you is who was first to a thread basically in my experience, and I had over 500k of it lol it's nothing though I could go troll for days before making a dent in the 10k you get from an obvious joke on the new tab and then the thread takes off
Best way to tell if someone is a troll is just to look at what they say imo 🤷🏻♂️
I had my third party app and browser extensions set to automatically hide comments by people with very low karma and very low comment scores. I'd only ever see hateful comments if I clicked to unhide them and I liked that
Idk I felt like above a certain point karma was just an indication that that person knew how to game the system and play nice with reddit.
I like how it is on lemmy. I feel like downvotes/upvotes prompt conversations. You're at 47/6 and it doesn't really matter to me, it just shows that people might not totally agree and then I'm hopeful that they have left a comment.
I think it's also possible that the voting system on reddit was effective at marginalizing people.
You can only lose about 100karma in one comment thread so if a troll can get one high upvote comment it can counteract literally 100's of negative comments.