Comments lack the body language that convey a lot of meaning and context. Some estimate over 90% of effective communication is from non-verbal queues such as reassuring smile.
There are also 'historical' or 'cultural' elements that can come into play. As a fictitious example, if someone had a posted a comment like 'clean your browser cookies - we know what you've been up to, nudge nudge, know what I mean, know what I mean?". Someone unfamiliar with Monty Python comedy might not get the reference and potentially interpret that to be something directed personally at them and full of chiding recrimination. Whereas, the poster may have been light-kindheartedly offering a tip about how this is happening and was trying to make the poster laugh in the middle of all of this by calling to mind a famous comedy sketch. Laughter being the goal, not derision.
I see a lot of people sincerely hoping you stick around; I am one of them. If a comment is not clearly capricious or viscous, I hope you give commenters the benefit of the doubt. Maybe they didn't mean it that way. Maybe they did but they are having a bad day (or a bad life???). Maybe if it is not crystal clear, its worth erring on the side of caution since there are a lot of great folks here on the DP and an actual community. As far as nasty trolls go, this site is a lot different than some others I've seen on the net.