I agree that one of the first steps towards making Steemit a better place is by not rewarding spam comments, and that takes work since it's not always easy to tell the difference between bots and people who are non-native speakers. 😞
As you said, that requires READING!
And then there are the "Thanks for sharing. Resteemed" comments as you point out. I usually look at the commenter profile if in doubt, and if it's someone who's been around and also makes quality posts, sometimes I might reward that. At the end of the day, it's very subjective . . . unless you're a bot. 😅